It takes a great deal of effort to prepare food. Animals eat their food raw, in its natural state, but this is insufficient for man, whose nature is far more refined and complex. Man must produce his own food. First he must prepare the ground. He must remove the stones, and then plow, plant, weed, and prune. Yet even after the wheat has ripened, it is still not fit to be eaten. In order to obtain the edible kernels, he must thresh and winnow. Even then, the grains remain inedible until they are cooked. To make bread, he must go further: He must grind the kernels, remove the chaff, sift the flour, knead the dough, and bake it.
Had Adam not sinned, food preparation would have been effortless and simple. Man would have gone into the field, plucked delicious baked goods and rich foods off the trees, and eaten them (see Kiddushin 82a.). If he felt like it, he could work a bit in the field and season his food to taste. The Sages inform us that in the future, after we have rectified Adam’s sin, we will return to this state (Shabbat 30b). Delicious baked goods and pretty clothes will grow on trees in Eretz Yisrael. But in the meantime, man must toil and struggle in order to produce even a single loaf of bread. This accords with God’s statement to Adam after the sin: “The land is cursed on your account. In sorrow you will eat from it all the days of your life. It will bring forth thorns and thistles for you, and you will eat the plants of the field. By the sweat of your brow you will eat bread until you return to the ground” (Bereishit 3:17-19).
The sin caused all of nature to deteriorate, and what grows from the earth is often insufficiently pure and evolved to consume in its natural state. Man must perform many steps to turn the earth’s produce into edible food. But on Shabbat we ascend to a level that approaches the World to Come; we connect to a level beyond sin, beyond the need to work in order to improve the world. This enables us to understand the inner significance of all melakhot. With this knowledge we can improve the world.
There are eleven melakhot connected to growing food: sowing (Zore’a), plowing (Ĥoresh), reaping (Kotzer), gathering (Me’amer), threshing (Dash), winnowing (Zoreh), separating (Borer), grinding (Toĥen), sifting (Meraked), kneading (Lash), and cooking/baking (Bishul/Ofeh).
Three additional melakhot are necessary to produce animal-based foods: trapping (Tzad), slaughtering (Shoĥet), and skinning (Mafshit). We will begin with the melakha of Bishul, as it is most relevant to us today.
Bishul is the melakha that prepares or improves food, whether through seething, baking, or roasting. What defines this melakha is that food is prepared by means of fire’s heat. The food is softened by the heat, and the tastes within it merge to create a new taste, which is intense and contains a variety of flavors.
Cooking initially softens food, and most foods remain soft after being cooked. However, there are some foods that harden in the course of cooking, like eggs. Similarly, the process of roasting softens the food at first, but eventually makes it tougher.
Torah law prohibits cooking, and this prohibition even includes foods that can be eaten raw, if cooking improves them in some way. For example, although one can certainly drink cold water, nevertheless, since cooking improves the water, doing so is prohibited by Torah law. Cooking foods that are not improved by this process is not prohibited by Torah law, but it is still prohibited rabbinically (MT 9:3; SHT 318:114).
One who cooks using fire or something that was heated by fire (toldot ha-esh) transgresses a Torah prohibition. Therefore, if one heats a frying pan on the fire, then turns off the fire and fries an egg in the hot frying pan, he has transgressed a Torah prohibition. This is the case even though the pan was no longer on the fire during the actual frying (SA 318:3; MB ad loc. 17; concerning cooking in the sun, see section 25 below).
Any accepted form of cooking is prohibited by Torah law. Therefore, one who cooks in a microwave transgresses a Torah prohibition, because nowadays this is one of the normal ways of cooking (Igrot Moshe, OĤ 3:52).
Before we explain the laws of Bishul in detail, we will preface them by saying that there are three types of prohibitions relevant to Bishul:
Bishul by Torah law;
Rabbinic enactments that forbid doing anything that might cause someone to turn up a flame (laĥatot ba-geĥalim, literally, “to stir the coals”);
Rabbinic enactments that forbid doing anything that resembles cooking.
To determine whether one may do a particular action, he must examine it from these three perspectives. To elaborate:
One must clarify if this action is forbidden because it qualifies as Bishul. Any action that leads to food’s transformation from a raw state to a cooked state is prohibited by Torah law. (This prohibition and those deriving from it will be explained in sections 3-13 below.)
From the perspective of the Torah prohibition of Bishul, one may leave food on the fire when Shabbat begins, with the intention that it will continue cooking on Shabbat. However, the Sages prohibit doing so when it may be necessary to adjust the heat, due to the concern that one may forget it is Shabbat and turn up the flame, thus transgressing the Torah prohibitions of Mav’ir and Bishul. But if the fire is covered, as it is in the case of a plata (warming tray), one may place food on it, because there is no chance that he will forget it is Shabbat and turn up the flame.
Even if a food is fully cooked, and thus there is no concern that one will turn up the flame, the Sages still forbid doing anything that looks like cooking. Therefore, one may not put fully-cooked cold food directly on the fire. However, one may put such food far from the heat source, in such a way that it does not look like cooking. (As we will explain in sections 18-21, there is disagreement whether placing food on a plata looks like cooking and is thus forbidden.)
A fundamental rule of the laws of Shabbat is that one may not create a new entity. During the other six days of the week, we emulate God, in whose image we were created, by busying ourselves with creating and developing. We take the raw materials of the world and develop and improve them, thus continuing the work of creation. Just as the Creator ceased creating on Shabbat, so too, we are commanded to emulate God’s attributes by establishing Shabbat as a day of holiness and rest. It is a day when we desist from creating new things, and thus enable ourselves to contemplate the world as God created it and increase our faith.
This principle is the principle behind Bishul as well. Cooking is forbidden because it changes a food from raw to cooked, thus giving it a new identity. But if the food is already cooked, there is no prohibition of reheating it, as reheating does not create a fundamentally new substance. Even when the reheating improves the taste, it is still not prohibited, following the accepted principle: ein bishul aĥar bishul (there is no prohibition of cooking something that has already been cooked). Therefore, the following question is critical to the laws of Bishul: When is a food deemed cooked? If it is considered cooked, then one may reheat it on Shabbat, and if it is not considered cooked, one may not do so.
Some of the greatest Rishonim disagree on this question. Some maintain that if the food can be eaten in a pinch, Bishul no longer pertains to it. However, in practice, it is agreed that a food is considered cooked only when it is fully cooked and one could serve it to guests without feeling compelled to apologize. Before that point, even if one could technically eat it in a pinch, it is not considered cooked (SA 318:4). Therefore, in practice, it is important to determine whether a food is mevushal kol tzorkho (fully cooked). As long as it is not mevushal kol tzorkho, any action undertaken to raise its temperature and speed up the cooking process is prohibited by Torah law.
For example, the heat of a plata is often uneven; there are hotter and cooler places on its surface. One may not move a food that is not yet fully cooked from its current place to a hotter place on the plata. Similarly, one may not put a towel over the food to contain the plata’s heat more effectively. Furthermore, if one removes the cover of a pot in order to check if the food is fully cooked, and it becomes clear that it is not, it is now forbidden to replace the cover, because doing so will make the food cook faster.
However, if the food is fully cooked, one may move it to a hotter place, and if he took off the cover he may replace it. Furthermore, one may cover the pot with a towel to preserve its heat. One may do so even if it improves the food’s taste, as it does with cholent. Similarly, one may remove fully-cooked meat from the freezer and heat it (in a way that does not resemble cooking; see section 18). For it is an accepted principle that after a food is classified as cooked, it is no longer prohibited to reheat it. (All of this refers to solid foods; liquids involve additional issues that we will expand upon in sections 5-6.)
Cholent is considered fully cooked even if the bones in it are not soft, and one may cover it to preserve its heat. However, if one is accustomed to eat the bones, then as long as they are not yet cooked the food is not deemed fully cooked, and one may not cover it and preserve the heat.
. According to Rambam, Teruma, Smag, Smak, Hagahot Maimoniyot, Or Zaru’a, Riva, and Tur, as long as the food is not fully cooked, cooking it is prohibited by Torah law. According to Ramban, Rabbeinu Yona, Rashba, Rosh, and Me’iri, once a food has reached the state of ma’akhal ben Derusa’i (see n. 14), the principle of ein bishul aĥar bishul applies. The bottom line is that, according to SA 318:4, only once a food is fully cooked does the principle apply. BHL 318:4 s.v. “afilu” states that those who prohibit the further cooking of a dish that has reached the state of ma’akhal ben Derusa’i maintain that it is a Torah prohibition. However, Eglei Tal, Ha-ofeh 7:16 maintains that most of those who forbid this see it as a rabbinic prohibition. Be-di’avad, if one cooked something on Shabbat that had reached the state of ma’akhal ben Derusa’i before Shabbat, it may be eaten on Shabbat. This is because when it comes to the question of benefiting from the result of a melakha, one may rely on the lenient opinion (below 26:5).Cholent with chicken bones: According to R. Shlomo Zalman Auerbach, if chicken bones in a cholent are not fully cooked, the whole cholent is considered not fully cooked, since most people eat the chicken bones that were softened by extended cooking. Therefore, even those who do not eat the bones must be stringent and not take any action that will heat cholent that contains partially cooked bones (Minĥat Shlomo §6; SSK 1:20). In contrast, R. Moshe Feinstein maintains that since most people do not eat these bones, one need not take them into account; as long as the cholent as a whole is fully cooked, one no longer has to worry about Bishul. Only in the case of an individual who generally eats the bones would the cholent be considered not fully cooked when the bones are not fully cooked (Igrot Moshe, OĤ 4:76-77; Yalkut Yosef 318:78). Nowadays, since most people do not eat the bones, the cholent is normally considered cooked even if the bones are not.
A fundamental issue in the laws of Shabbat is establishing the temperature of yad soledet bo (the temperature at which the hand recoils). The Sages state that this is the minimum temperature that is still capable of cooking food. However, it is uncertain precisely what this term refers to. Does it refer to a level of heat that the hand can only stand to touch for a few seconds? If so, this would be approximately 71° Celsius. Alternatively, does it refer to a level of heat that becomes unpleasant for one’s hand after a few minutes? If so, this would be approximately 45°C.
According to many poskim, since the matter remains in doubt, one must be stringent. Heat of 45°C must be considered capable of cooking. Thus, one may not put raw food into a pot that has reached a temperature of 45°C or higher. Similarly, one may not place raw food near enough to a fire that it could reach 45°C or higher (SSK 1:1).
This definition is also important for how the laws of Bishul apply to water. One may not raise the temperature of water from below yad soledet bo to yad soledet bo or higher. However, if the water has already reached yad soledet bo, it is considered cooked, and one may continue to heat it further, because of ein bishul aĥar bishul. Cold water may be left near the plata as long as the water is in a place where it would not reach yad soledet bo even if it remained there for an entire day.
Thus, in practice, one must be careful not to heat water to between 45°C and 71°C; since we do not know the precise temperature of yad soledet bo, any heating in that range may be considered Bishul. But one may heat outside of this range. For example, if water has been heated to 71°C, one may then put the water in a place where it will get hotter, because of ein bishul aĥar bishul. Similarly, one may put cold water in a place where it will heat up, as long as the water does not exceed 44°C, because this kind of heating does not qualify as Bishul.
There is another important position that defines yad soledet bo. This position maintains that food or drink that most people would be able to consume all at once cannot be considered yad soledet bo. However, if most people would be unable to eat or drink it all at once, that is a sign that it is yad soledet bo. Thus, it would be considered cooked, and one may heat it further (Ben Ish Ĥai, Year 2, Bo 5; Maharsham 1:187; Yabi’a Omer 3:24, 4-6). In a case of necessity, one may rely on this position.
To create a safeguard, the Sages prohibited leaving water in a place where it could potentially reach yad soledet bo, even if one is standing there watching and waiting to remove the water before it reaches that point. They were concerned that the person watching might get distracted and forget to remove the water before it reaches yad soledet bo, thus making him guilty of cooking on Shabbat. However, if there is no possibility that the water will reach yad soledet bo even if it remains there for an extended period of time, one may place the water there (SA 318:14).
. Igrot Moshe, OĤ 4:74:3 states that the temperature of yad soledet bo is somewhere between 43°C and 71°C. According to Or Le-Tziyon 2:30:12, it is between 40°C and 80°C, based on the notion that at 40°C a baby’s belly is scalded. This measurement is mentioned in SA 318:14. At the other extreme, some people drink tea that is as hot as 80°C. SSK states, based on a proof suggested by R. Shlomo Zalman Auerbach, that the lowest possible temperature for yad soledet bo is 45°C. Even though most poskim feel that one should be stringent and take into account both versions of yad soledet bo (that the hand cannot bear to remain on the heat source, or that it is merely unpleasant for the hand to remain), it is not necessary to follow the extremes within these positions. This is why I wrote that between 45°C and 71°C constitutes the doubtful range. Furthermore, if necessary one may rely on the position that uses the criterion of whether the food can be eaten or drunk all at once. There are some who are stringent and refrain from heating water even if it is already yad soledet bo. See SSK ch. 1 nn. 17 and 110. In contrast, Ashkenazic custom is that if the hot water started out at yad soledet bo and later cooled down, as long as it is still a little warm one may bring it back to a boil. (See the continuation of this discussion in sections 5-6.). According to Rashi and Rambam, one may place water in a place where it could become yad soledetbo on condition that someone is watching it to ensure that this will not happen. However, Tosafot, Rosh, Rashba, and most poskim maintain that this is forbidden, and this is the ruling of SA 318:14. In contrast, if one wishes to heat a cold liquid that had previously been cooked, like soup, one may be lenient and place it where it could reach yad soledet bo as long as someone is watching it and waiting to remove it before it reaches that temperature. This is permitted because (as we will explain in the next paragraph) according to Rambam, Rashba, and Ran, the principle of ein bishul aĥarbishul holds even for a liquid. This situation is considered a twofold doubt: first, perhaps the law really follows the lenient position of Rashi and Rambam; second, perhaps ein bishul aĥar bishul applies to liquids as well. R. Ovadia Yosef writes in Livyat Ĥen §51 that one may be lenient as a result of this twofold doubt. It is true that some are stringent in this case (SSK 1:13; Menuĥat Ahava 2:10:5; and Orĥot Shabbat 1:18) and are willing to endorse leniency only in a case of great need. Nevertheless, the primary position is to be lenient. This is because even according to those who are stringent and maintain that einbishul aĥar bishul does not apply to liquids, if one forgot to remove the liquid before it reached yad soledet bo he will only have transgressed a rabbinic prohibition, since he did not intend to boil the soup but only to heat it a bit.
We have already learned that there is no prohibition of cooking something that has already been cooked. Therefore, one may reheat cooked food on Shabbat. For example, one may remove cooked fish or fried schnitzel from the refrigerator and reheat them to yad soledet bo, as long as it does not resemble cooking (see section 18).
But there is a fundamental disagreement among the Rishonim whether this principle applies to liquids like soups and sauces. For this purpose, a liquid is something that, if left in a bowl, would spread out evenly. If it retains its shape, it is considered a solid. According to Rambam, Rashba, and Ran, the principle of ein bishul aĥar bishul applies to cooked soup as well. Therefore, based on their opinion, one may take soup from the refrigerator on Shabbat and heat it, as long as it does not look like he is cooking (section 18 below).
However, according to Rashi, Rosh, Smag, and Smak, the principle of ein bishul aĥar bishul applies only to solid food, and one may reheat them on Shabbat. Liquids, on the other hand, even if they had been fully cooked, may not be reheated once they have cooled off, and doing so is considered Bishul. This is because when it comes to solid foods, the primary purpose of cooking them is to create the cooked or baked taste. Once bread is baked, the difference between eating it hot or cold is insignificant. The same is true of fish and potatoes; it makes little difference whether they are served hot or cold. Therefore, from the moment that these foods acquire a cooked or baked taste, their cooking is considered complete. Accordingly, even if they have cooled off, one may reheat them, because cooking no longer affects them significantly. But for liquids, their temperature is an integral part of defining them as cooked. There is a fundamental difference between cold soup and hot soup, and the same is true of tea and coffee as well. Therefore, for liquids, we say yesh bishul aĥar bishul (there is a prohibition of cooking something that has already been cooked). Thus if a liquid has cooled down, one who reheats it to yad soledet bo transgresses the Torah prohibition of cooking.
Shulĥan Arukh rules in accordance with the stringent opinion (318:4), and Sephardim follow this ruling. Thus, for Sephardim, if a cooked liquid has cooled down to below yad soledet bo, it is no longer considered cooked, and it is prohibited by Torah law to reheat it past yad soledet bo. Therefore, Sephardim may not take soup out of the refrigerator and heat it. Similarly, if they remove soup from the plata, and it cools off to below yad soledet bo, they may not replace it on the plata. If it is known with certainty that the liquid is still yad soledet bo, it may be replaced (as long as it meets the conditions explained below in section 19). If one had situated it near the edge of the plata (which tends to be cooler), he may move it to the center and thus heat it more effectively.
If most of the food in a cold pot is solid, but the pot also has liquid sauce or gravy, one may not heat the pot. This is because by doing so one will also be heating up the liquid, which would constitute Bishul. The way around this is to remove the solid food and heat it by itself. One does not need to worry about the little moisture remaining upon it. Similarly, one may reheat cold food like meat or fish, even if there is a bit of wetness on them, because that liquid is not important and is batel (rendered insignificant) with respect to the solid food.
If food is congealed but will liquefy when reheated, like mushroom gravy, it is considered a solid food, and one may heat it (MB 318:100; Kaf Ha-ĥayim §158). However, according to Ashkenazic practice, le-khatĥila one should not heat it because some maintain that le-khatĥila one should not take an action that will cause food to change from liquid to solid or the reverse, because this is like producing something new (see 12:12 below). However, if the gravy is secondary to the solid food, then even Ashkenazic custom would permit le-khatĥila heating the food together with the congealed sauce or gravy, which will liquefy.
. From the language of SA 318:15 it would seem that if a food contains some liquid, even though it is mostly dry, one may not heat it because of the prohibition of cooking liquids. This also seems to be the understanding of MB 318:32 and 318:39, and SHT 60. It is also found in Or Le-Tziyon 2:30:13 in the note, and in R. Messas’s ResponsaTevu’ot Shemesh, OĤ 5. Opposing this position is Pri Megadim, Mishbetzot Zahav 253:13, which is lenient and follows the position that we consider the majority of the dish, since when there is only a little gravy, further cooking will be mitztamek ve-ra lo (detrimental to it). Additionally, according to Rabbeinu Yeruĥam, in such a case one may even cook a liquid. This is also the opinion of Minĥat Kohen and others cited by Yabi’a Omer 6:48. (However, Yalkut Yosef 318:55 states that one who chooses to be stringent should be commended, and in R. Ovadia’s book Ma’or Yisrael, p. 17 it seems that he permits reheating only if the sauce is thick.) In contrast, some are stringent and feel that according to SAH, anything that is tofe’aĥ al menat le-hatfi’aĥ (wet enough to make something else wet) is considered a liquid, and heating it is forbidden. (See Ketzot Ha-shulĥan 124, Badei Ha-shulĥan 37; Shabbat Ke-halakha, pp. 141-144.) The halakha follows the middle position, as explained above. It should be noted that the custom in North Africa was either to be lenient in accordance with Rambam, Rashba, and Ran, maintaining that ein bishul aĥar bishul applies even to liquids, or minimally to follow the Ashkenazic custom that if the food is still a bit warm, one may warm it up, as cited in the next paragraph below (Tashbetz; Shemesh U-magen 1:8).
As we have seen, according to Rambam, Rosh, and Ran the principle of ein bishul aĥar bishul applies to liquids as well as solids. Thus as long as the liquids were fully cooked, even if they have now cooled off, one may reheat them to yad soledet bo.
There are many Yemenite Jews who consistently follow Rambam’s rulings throughout halakha. Therefore, if they serve soup Friday night and then put it in the refrigerator, they may remove the soup from the refrigerator on Shabbat day and reheat it. This is the law for sauces and all other liquids as well.
Ashkenazim follow Rema, whose opinion is a kind of compromise between the previous two. If a liquid has cooled off to the point that one normally would therefore not consume it, then one may not reheat it to yad soledet bo. But if it is still warm, one may reheat it to yad soledet bo. This is because Rema fundamentally accepts the position of Rambam that ein bishul aĥar bishul applies to liquids as well. However, in his opinion, if a liquid has cooled down entirely, it is rabbinically forbidden to reheat it.
When one who follows the position of Shulĥan Arukh or Rema is a guest at the home of a Yemenite who follows Rambam, he may eat soup that his host heated on Shabbat. Since the host is following halakha based on the accepted practice of his community, any Jew may eat his food le-khatĥila (see MB 318:2.).
However, one who follows the Shulĥan Arukh or Rema may not ask one who follows Rambam to heat soup for him. Since his own community forbids reheating soup, he may not ask his friend to do it for him. But if he invites his friend to eat with him, his friend may follow his own custom and heat soup for himself. In such a case, the host may eat from it as well.
. This is explained in Nishmat Adam 20:8; Ĥazon Ish, OĤ 37:13; and Igrot Moshe, OĤ 4:74:2. The rationale is either that it resembles cooking, or that we are afraid that people might come to actually cook. Some maintain that according to Rema, if the soup has cooled down entirely, it would be prohibited by Torah law to reheat it (see MA 253:37; Tehila Le-David §33). The logic behind this is that as long as it is still warm and can still be eaten as a hot food, it is still considered cooked. However, if it has cooled down entirely and can no longer be considered warm, then its original cooking has been nullified, and the prohibition of cooking applies to the food once more. (One could suggest that as long as it remains warm, it is considered a ma’akhal ben Derusa’i. See Eglei Tal 14 and Shabbat Ke-halakha, pp. 136, 182.)
Cooking is normally done by putting food into a vessel that is on a fire. The question arises: If one has a pot that is not on a fire or on a plata, but that contains a liquid that is yad soledet bo or hotter, may one place uncooked food into this hot liquid?
In halakha, only certain types of vessels are considered capable of cooking, while others are not considered capable of cooking. In order to elaborate on this idea, we must first define several terms. A kli rishon is a pot or pan that has been heated on the fire. A kli sheni is a pot or pan into which water or food from a kli rishon has been poured. There is a halakhic difference between a kli rishon and a kli sheni. Since a kli rishon was on the fire, the walls of the pot became heated from the fire directly. Therefore, it retains its heat for a long time, and can cook raw food that is placed in it. In contrast, the walls of a kli sheni were not heated directly by fire, so the water or food placed in it cools down quickly. Thus, a kli sheni is not capable of cooking raw food that is placed in it (Tosafot, Shabbat 40b, s.v. “shema mina”).
However, there are some foods, including certain types of fish, that are unique in that they cook quickly and easily. These foods, known in halakhic literature as kalei ha-bishul (easily cooked), can become cooked even in a kli sheni. Thus, cooking kalei ha-bishul is prohibited by Torah law even in a kli sheni. In addition, even irui (pouring water over them) from a kli sheni is forbidden. Since kalei ha-bishul are so easy to cook, even this can cook them and render them edible (MB 318:36).
In principle, it would seem that only a few foods truly qualify as kalei ha-bishul. Nevertheless, some prominent poskim were concerned that we do not know how to differentiate between kalei ha-bishul and regular foods. According to them, only if we know explicitly that a particular food is not included in kalei ha-bishul, like water or oil, may it then be heated in a kli sheni (MB 318:42; SSK 1:59). Additionally, according to some prominent poskim, it is rabbinically prohibited for food that was not cooked before Shabbat to be placed in a kli sheni on Shabbat, because this resembles cooking (MA; MB 318:34). Therefore, in practice one should not place food that has not already been cooked into a kli sheni, but irui from a kli sheni onto an uncooked food is only prohibited when one knows for certain that a specific food is among kalei ha-bishul.
Therefore, one may prepare an instant soup mix by pouring water from a kli sheni into the dry mix. However, one may not prepare instant mashed potatoes this way, because doing so violates the prohibition of Lash (see 12:7 below).
There is a third type of vessel known as a kli shlishi. If one pours hot water or hot food from the pot in which it was cooked into another vessel, and from that vessel into a third one, that final container is a kli shlishi. The poskim agree that a kli shlishi is unable to cook anything.
. In truth, some Aĥaronim were inclined to be stringent and avoid putting anything raw and easily cooked into a kli shlishi that is yad soledet bo. Thus states Shevitat Ha-Shabbat, Mevashel 23, based on Yere’im. This is also the position of Ĥazon Ish regarding kalei ha-bishul (ĤazonIsh, OĤ 52:19). He maintains that as long as the water is hot, no matter how many times removed the vessel is from the original kli rishon, kalei ha-bishul become cooked. AHS 318:28 states this specifically with regard to tea. According to Ĥayei Adam 20:4, any vessel whose contents are so hot that they would burn someone is capable of cooking. However, according to most poskim, the principle that Bishul does not apply in a kli shlishi is absolute, and any kind of raw food may be introduced into a kli shlishi. MB 318:47 records this based on Pri Megadim. The accepted explanation is that this was the Sages’ assumption – cooking is inconceivable in a kli shlishi. Further, it seems to me that cooking in a vessel that people do not generally use for cooking would not be prohibited by Torah law, since the Torah prohibition applies only to cooking in the usual manner. Since one normally does not cook in a kli sheni, there is no Torah prohibition of putting raw food into a kli sheni. However, foods that cook easily are often cooked in a kli sheni or even by irui from a kli sheni. Therefore, if one places these foods in a kli sheni or pours water on them from a kli sheni, he transgresses a Torah prohibition. However, not even kalei ha-bishul are generally cooked in a kli shlishi, so there is never a Torah prohibition involved. And since in the vast majority of cases one cannot cook in a kli shlishi, the Sages did not prohibit cooking in one in any case.MA, MB 318:34, and Kaf Ha-ĥayim §70 state that the halakha follows the first opinion presented in Tosafot, Shabbat 39a. This opinion states that even though a kli sheni does not cook, one may not place raw food into such a vessel because it resembles cooking. One may, however, add spices, since that does not resemble cooking. This is also the position of Or Le-Tziyon 2:30:5. In contrast, R. Ovadia Yosef, basing himself on a number of Rishonim and Aĥaronim, writes that the halakha follows the second opinion in Tosafot, according to which there is never a concern of resembling cooking in a kli sheni (Yeĥaveh Da’at 6:22).
Some maintain that since we do not know what foods are considered kalei ha-bishul, we must be stringent and refrain from putting any foods into a kli sheni except those that we know are not kalei bishul (Yere’im; Smag). Others maintain that only specific foods that are known to be kalei ha-bishul are a concern (Ran; Tur). Rema 318:5 states that the custom is to be stringent, as do MA 318:18; SAH 318:12; Ĥayei Adam 20:4; MB 318:42; SSK 1:59. SA 318:5 cites both opinions and seems inclined to be lenient. This was the inclination of a number of poskim – that one need be stringent only with foods that are known to cook easily (Ĥazon Ish, OĤ 52:18; Or Le-Tziyon 2:30:3). Yalkut Yosef 318:47 also records this as the position of Rambam and Maharam ibn Ĥabib.
To simplify the matter, I wrote to be consistently stringent in the case of a kli sheni, and consistently lenient in the case of a kli shlishi. Even though it is agreed that one may not pour from a kli sheni onto kalei ha-bishul, nevertheless we have seen that according to most poskim, most foods are not kalei ha-bishul. Moreover, even those who are stringent consider the prohibition rabbinic, since one does not intend to cook. Additionally, pouring will only cook the outer layer of the food, which is less than the amount required to transgress a Torah prohibition, and according to Rashbam this is not considered cooking at all. Therefore, one should only be stringent and refrain from pouring from a kli sheni in the case of foods that are known to be kalei ha-bishul.
One who wishes to prepare tea using a tea bag must do so in a kli shlishi. This means that he must first pour the hot water into a cup (which becomes a kli sheni). Then, from this cup, he must pour the water into another cup, which becomes a kli shlishi. He may then place a tea bag in the water.
At first glance, it would seem that one should be allowed to do this even in a kli sheni, since the rule is that a kli sheni cannot cook. However, as we established, even a kli sheni can cook kalei ha-bishul, and some are concerned that tea leaves fall into this category. Additionally, others believe that there is a rabbinic prohibition on placing uncooked food into a kli sheni because it resembles cooking (MA; MB 318:34). Therefore, one who wishes to prepare tea must do so in a kli shlishi.
Some are even more stringent. They maintain that since we see that a tea bag releases color and flavor into the water even in a kli shlishi, this is an indication that tea cooks very easily, and therefore one may not put it even in a kli shlishi (AHS; Ĥazon Ish). However, according to the majority of poskim, the rule that a kli shlishi does not cook is absolute, and one may always put uncooked food in a kli shlishi. Additionally, just because a tea bag releases color and taste in a kli shlishi does not prove that it has been cooked. The fact is that even if you put a tea bag in water that is only 40°C and not hot enough to cook at all, the bag will still release color and taste. Therefore, one may put a tea bag into hot water in a kli shlishi.
If one prepared tea essence before Shabbat, one may pour it into hot water in a kli sheni. This is because the essence is not considered kalei ha-bishul, so pouring it into the cup does not resemble an act of cooking.
Those who are especially meticulous, and avoid coloring foods le-khatĥila (see 12:10 below), should pour the essence into a kli shlishi and pour water onto it from a kli sheni. In this manner, the essence does not play an active role in coloring the water. All agree that in such a case there is no issue of coloring.
If the tea essence gets used up on Shabbat, and only tea leaves remain with no liquid, one may prepare new essence by pouring hot water from the urn into a cup, which becomes a kli sheni, and from there pouring the water onto the tea leaves. This is not considered cooking, because the tea leaves were already cooked before Shabbat.
. As we learned at the end of the previous note, one should not place tea leaves in a kli sheni, out of concern that it resembles cooking. Similarly, we must take into account the possibility that tea leaves are kalei ha-bishul, which may not be placed in a kli sheni. Even pouring onto them from a kli sheni is prohibited. But if the leaves are inside a tea bag, one may pour onto them from a kli sheni. This is because pouring only cooks the outer layer, so the leaves inside the bag will not be affected (Or Le-Tziyon 2:30:3; Yalkut Yosef 318:41).As I wrote above, if the liquid of the tea essence prepared before Shabbat is running out, one should pour hot water from a kli sheni onto the cooked tea leaves. Since the leaves were already cooked before Shabbat, there is no longer a prohibition of cooking them. Pouring water directly from the urn into the container of the essence is prohibited, since the liquid of the essence has already cooled down, and many poskim maintain that one may not heat them to yad soledet bo in such a case (see section 5 above; MB 318:39). Furthermore, perhaps the tea leaves did not cook entirely before Shabbat, in which case pouring the water on them will complete their cooking. But irui from a kli sheni is certainly not cooking in this case. Even if we are concerned that the leaves are considered kalei ha-bishul, since they were already cooked before Shabbat there is no concern that pouring from a kli sheni will continue to cook them. One also does not need to worry about cooking the cold water left with the leaves, because water is definitely not included in kalei ha-bishul.
Halakha is unique in its precision and its focus on even the tiniest details. This precision elevates all our activities and gives them spiritual meaning and value. It should come as no surprise, then, that the Torah prohibition of cooking applies not only to large quantities of food, but even to the smallest drops of water. Because of this, some maintain that one may not pour hot water from an urn into a cup that has droplets of cold water inside, because the hot water will cook the cold water. Therefore, one must thoroughly dry out the cup, and only afterward may one pour hot water into it (Igrot Moshe, OĤ 1:93; Minĥat Yitzĥak 9:30; SSK 1:52).
In contrast, many poskim maintain that it is unnecessary to dry the cup, because this pouring is not a normal way of cooking. Also it is doubtful whether in fact the drops will cook. Even if they do, the person does not intend for them to cook, nor does he know if they have cooked. His intent when he pours the water has nothing to do with these droplets. The halakha follows this approach (Tzitz Eliezer 13:40; Shevet Ha-Levi 7:42; Yabi’a Omer 4:33).
. It is true that during Temple times, in order to be liable for a sin offering for cooking on Shabbat, one must have unknowingly cooked a quantity of water that would be at least enough to rinse a small limb (MT 9:1). Nevertheless, cooking even one drop is still prohibited by Torah law. This is at the heart of the opinion of those who are stringent in our case. Even though the droplets of moisture are in a kli sheni, nevertheless the hot water was poured from a kli rishon, and the consensus is that this cooks the outer layer of the food.On the other hand, there are many reasons to be lenient in this case. Since these drops are not being cooked in the normal way, the prohibition is rabbinic. Since one does not benefit from the results of this cooking, it is considered a psik reisha de-lo niĥa lei, which some permit in the case of a rabbinic prohibition. Furthermore, this might not even be a psik reisha, since the poured water might not reach the drops directly (see above ch. 9 n. 2). Additionally, according to Ĥakham Tzvi §86, since the reason halakha forbids ĥatzi shi’ur (violating a prohibition below the threshold of punishment) is that the person has subjectively deemed it important, when he does not intend the prohibited result there is no violation even if it is a psik reisha. Tzitz Eliezer 13:40 states similarly that these drops have no importance. Moreover, we can add to the equation the position of Rashbam that irui from a kli rishon does not cook. Also, if the moisture in the cup is from hot water that has cooled down, some permit this, applying the principle of ein bishul aĥar bishul here (see sections 5-6 above). In practice, since even those who prohibit this admit that it is a rabbinic prohibition (since the one pouring the water is not interested in cooking the drops), the halakha follows those who are lenient. Based on most of the reasons presented here, there is no need to dry off a spoon that one wants to use to remove food from a kli rishon (Shevitat Ha-Shabbat, Introduction to Mevashel 19; Tzitz Eliezer 13:40).
Some are concerned about allowing the use of an electric urn that has a tube running down the side that displays how much water is inside. The fear is that as the water in the urn is used up, some of the water from the tube enters the urn; if this water was cold it will be cooked by the hot water in the urn. But many are lenient about this. First, the person does not intend for this to happen. Additionally, it may be that the water in the tube was already yad soledet bo. Even if this is not the case, it might have been cooked to yad soledet bo before Shabbat. Then, according to those who maintain that ein bishul aĥar bishul applies to liquids (see sections 5-6), one may reheat it on Shabbat (Az Nidberu 9:14; Yeĥaveh Da’at 6:21).
As we stated in section 7, a kli rishon can cook anything, a kli sheni can cook only kalei ha-bishul, and a kli shlishi cannot cook at all. However, the poskim disagree regarding the status of a davar gush (hot, solid food).
Some maintain that the general rules of vessels apply in this case as well, and once a davar gush is moved to a kli shlishi it cannot cook anything that is placed upon it. This is the opinion of the majority of poskim (Rema; Vilna Gaon; Pri Megadim; Ĥatam Sofer; Nishmat Adam).
However, some poskim are stringent and rule that the aforementioned principles apply only to liquids or soft foods that come into complete contact with the walls of a pot. Such foods can no longer cook if they are transferred from a kli rishon to a kli sheni and from a kli sheni to a kli shlishi. But chunks of solid food – pieces of meat, kugel, potatoes, or clumpy rice – retain their heat even when transferred from vessel to vessel, as the walls of the new vessels do not have a strong cooling effect on solid food. Therefore, as long as these foods remain at a temperature of yad soledet bo or hotter, they are able to cook, no matter how many vessel transfers they have undergone (MA; MB 318:45).
In practice, since this relates to a Torah prohibition, it is appropriate to be stringent. However, if one is in doubt about whether cooking would be involved, one may be lenient even le-khatĥila. Therefore, if one can touch the piece of food and it is doubtful whether it is yad soledet bo, there is no need to worry that it will cook (see section 4 above). Even if it is clear that it is still yad soledet bo, one may put previously-cooked cold gravy on it, since some maintain that ein bishul aĥar bishul applies to liquids as well (see section 5 above). Similarly, one may salt the food, since salt can only be cooked in a kli rishon that is on the fire (MB 318:71). Additionally, one may place pickles or raw vegetables on a hot piece of kugel or meat, because one does not intend to cook them.
In contrast, one may not sprinkle raw spices like paprika and pepper on a hot piece of meat or kugel, as there is a benefit to the spices cooking – it enables their taste to be absorbed more effectively into the food. Therefore, before adding spices to a hot dish, one should wait until it has cooled off enough that one can touch it.
. Regarding the laws of kashrut, some are stringent in the case of a davar gush if it is still yad soledet bo. This is the approach of Isur Ve-heter, Maharshal, Shakh, Pri Ĥadash, and Pri Megadim. Opposing them are Rema, Vilna Gaon, and Ĥatam Sofer, based on Tosafot and Ran, who insist that a davar gush is no different from other foods. Others maintain that we are stringent for kashrut purposes because a davar gush can absorb tastes; but for Shabbat purposes, since a davar gush cannot cook, there is no prohibition. This is the approach of Minĥat Yaakov 61:45; Pri Megadim, Mishbetzot Zahav, YD 97:14. Furthermore, Igrot Moshe OĤ 4:74, Bishul 5; R. Ovadia Yosef, Halikhot Olam, 4:12; and Or Le-Tziyon 2:30:16 state that one may be lenient. However, MA 318:45 is stringent concerning Shabbat as well as kashrut, as are MB 318:118 and SSK 1:64. Since this disagreement relates to a Torah prohibition, it is proper to defer to those who are stringent, but in practice one need be stringent only regarding spices. In a case where there is an additional doubt, one may be lenient on the basis of the principle of twofold doubt. Similarly, one may be lenient regarding putting butter on a very hot solid, as the Igrot Moshe states, since butter is pasteurized, and pasteurizing is the equivalent of cooking. (SSK ch. 1 n. 198 disagrees, however.)
As we established in section 3, one may reheat fully cooked food on Shabbat, because the prohibition of Bishul applies when one changes the status of food from raw to cooked. However, once a food is cooked, one may reheat it. We must still clarify, though, whether one may change a food’s status from cooked to roasted, or from baked to cooked, etc. For example, may one take a piece of meat that was roasted before Shabbat and add it to the cholent pot? On the one hand, the meat is no longer raw, as it has already been roasted; on the other hand, adding it to the pot will change its status from roasted to cooked.
According to Raavya, Mordechai, and most Rishonim, this is permitted. Since the heat of the fire has already transformed the raw food to cooked, baked, or roasted, there is no longer a prohibition of Bishul. Further changing the status from roasted to cooked or vice versa is not considered Bishul but merely adding flavor, and this is not prohibited. This is the halakha according to some Sephardic poskim (Yeĥaveh Da’at 2:44; Menuĥat Ahava 2:10:26).
However, according to R. Eliezer of Metz, although one may reheat cooked, baked, or roasted food, one may not change a food’s status from roasted to cooked, because that is considered cooking it anew (Yere’im §274). Therefore one may not take baked bread and put it in a pot of food, because this would effectively change the bread from baked to cooked. Even if the hot food is in a kli sheni, one must take into account the possibility that bread is included in kalei ha-bishul and can become cooked even in a kli sheni. Thus the Ashkenazic custom is to be stringent (Rema 318:5). Some Sephardic poskim as well maintain that le-khatĥila one should be stringent (Ben Ish Ĥai, Year 2, Bo 6; Menuĥat Ahava 2:30:6).
However, even those whose practice is to be stringent agree that if be-di’avad one cooked something that had been baked, or baked something that had been cooked, one may still eat the food, since be-di’avad one may rely on the lenient opinion (MB 318:46).
Following the custom of most Jewish communities who are stringent in this regard, one who wishes to dip a cookie in tea or coffee must make certain that the teacup or coffee cup is a kli shlishi, since a kli shlishi definitely does not cook. One who wishes to dip bread in a bowl of soup may do so, as the ladle used to serve the soup can be considered a kli sheni and the bowl can be considered a kli shlishi (MB 318:45).
. Those who do not allow dipping bread into hot soup in a kli sheni follow two stringencies: a) They prohibit cooking after baking; b) they defer to the opinion that many foods are considered kalei ha-bishul and thus can become cooked in a kli sheni. Nevertheless, when serving soup using a ladle, according to Maharil, Pri Ĥadash, and others, the ladle is considered a kli sheni. Accordingly, the soup bowl is a kli shlishi, and in a kli shlishi there is definitely no prohibition. While Taz and Shakh maintain that the ladle is a kli rishon and MB 318:87 follows this approach, nevertheless this is a case of a twofold doubt, and thus one may be lenient (MB 318:45) as long as the ladle does not remain in the kli rishon long enough to reach the same heat as the vessel itself. Soup nuts may be added to a kli sheni even le-khatĥila, since they are deep fried and are considered cooked rather than baked (SSK 1:70). Furthermore, this further cooking is not desired, as people do not want the soup nuts to get soggy.According to those who maintain that ein bishul aĥar afiya (there is no prohibition of cooking something that has already been baked), one may definitely toast challah. Additionally, MA 318:17, Maĥatzit Ha-shekel, and Ĥayei Adam (Zikhru Torat Moshe 24:7) would permit this even for those who are stringent about bishul aĥar afiya, since they maintain that baking and roasting are the same. In contrast, some are stringent because they maintain that roasting is different from baking (Pri Megadim, Mishbetzot Zahav 318:7; SSK 1:71; Kaf Ha-ĥayim 318:78; Or Le-Tziyon 2:30:6; Menuĥat Ahava vol. 2 ch. 10 n. 154). There is even one opinion that expresses concern that this is considered Makeh Be-fatish (applying the finishing touch) (Rav Pe’alim, OĤ 2:52). In practice, the lenient position (that roasting and baking are the same) seems the more reasonable one, since if one continues to bake food it dries out, and essentially becomes toasted. Nevertheless, one who chooses to be stringent is commendable. This is the case when it comes to completely toasting the bread, but even those who are stringent would allow warming up bread – even to the point that the surface crisps – because doing so does not make a significant change to the baked state. Rav Pe’alim indeed states this in OĤ 2:52, and Nishmat Shabbat 318:26 states similarly.
Stirring food in a pot helps it cook better and more evenly, and therefore one who stirs food that is not fully cooked on Shabbat transgresses a Torah prohibition. The act of stirring is known in rabbinic literature as megis. Even if the food is no longer on the fire, as long as it is not fully cooked and it is yad soledet bo, it is forbidden by Torah law to stir it. In light of this, the Sages forbade removing food from a pot that contains food that is not yet fully cooked, even after the pot is removed from the plata, because the resultant movement in the pot would constitute stirring. Only when the food has cooled down and is no longer yad soledet bo may one remove the food he wants.
However, once the food has finished cooking and is ready to be eaten, there is no longer a problem of Bishul, and one may remove whatever he wants from the pot (SA 318:18). This is the custom of many Sephardim. In any case, one should not stir the food while it is still on the fire, because this resembles cooking (Yalkut Yosef 318:43).
The custom of Ashkenazim and some Sephardim is to be more stringent. As long as the food is still on the plata, even if it is fully cooked, le-khatĥila they do not remove any food. Rather, first they remove the pot from the plata and only then remove what they want. If they wish to return the pot to the plata afterward, they must be careful to follow the principles for returning food to the plata (section 19 below).
In cases of necessity, even those who are usually stringent are lenient, and allow fully cooked food to be removed from a pot on the fire. For example, if a pot is resting on an uncovered fire, so that if it is removed from the fire it will be forbidden to replace it (see section 19), one may remove food from the pot while it is still on the fire. This is because technically once the food is fully cooked there is no longer a prohibition of megis (Ĥazon Ish 37:15; SSK 1:38). Everyone agrees that if a pot or metal urn is filled with boiling water before Shabbat and then left on the plata during Shabbat, one may remove water from it on Shabbat (SSK 1:39).
. Those who are stringent defer to Kol Bo, which maintains that as long as the pot is resting on a heat source, whether flame or plata, stirring is forbidden by Torah law. Even though this position is problematic, and most poskim disagree with it, le-khatĥila we defer to it. This is the approach of Rav Pe’alim 3:45 and Or Le-Tziyon 2:30:15. (Perhaps they defer to this opinion because the activity of stirring resembles cooking.)
If the water in the cholent pot evaporates and one is concerned that the cholent will burn, one may not add cold water to the pot, because the water will become cooked. But if there is an urn on the plata, one may pour hot water from it into the pot. If the urn has a spigot designed to let the water out, one may remove the cholent pot from the plata and pour the hot water into it by means of this spigot. If the pot is designated for meat and the urn is designated for pareve, one should first uncover the pot for approximately ten seconds, so that the pot’s steam will dissipate. One may then move the pot under the spigot, since only minimal steam will be released. If it is difficult to pour directly from the urn into the pot, one may pour the hot water into a cup and then pour it from there into the pot. This is because as long as the water is yad soledet bo, according to the vast majority of poskim the prohibition of Bishul does not apply. This is the practice of the Ashkenazic, Yemenite, and North African communities (MB 253:84; Yalkut Shemesh §88; SSK 1:17).
Others maintain that one may not add hot water to a pot on the plata, because the primary issue is not how hot the water is, but the status of the water. While the water is still in the urn, it is considered a kli rishon. When one pours out the water, its status changes from a kli rishon (which has the ability to cook food) to irui from a kli rishon (which does not have the ability to cook). Then when the water reaches the pot, it is recooked, and can once again be considered a kli rishon. There are some Sephardim who follow this opinion (Yeĥaveh Da’at 4:22). If Sephardim wish to be lenient in accordance with the opinion of most poskim, they have an opinion to rely upon (Or Le-Tziyon 2:17:8; see Menuĥat Ahava 1:3:15).
. Poskim disagree about how to understand SA 253:4. According to MA 253:16, Eliya Rabba, Pri Megadim, and Eglei Tal, SA is lenient, maintaining that as long as the water is still yad soledetbo one may add it to the pot. In contrast, some maintain that SA is stringent, following the position of some Rishonim (the second explanation brought by Rabbeinu Yona and Rabbeinu Yeruĥam) that since poured water is no longer considered a kli rishon, and can cook only the outer layer of food, one may not turn the water back into a kli rishon. Thus states Lev Ĥayim 1:99, and Yeĥaveh Da’at 4:22 and Aseh Lekha Rav 6:28 conclude likewise. A practical suggestion for those who follow this position is to fill a bag with water, seal it well, and place it in the pot. If they see that the food is drying out, they can poke a hole in the bag and the hot water will spill into the pot.This entire stringency is only relevant for those who maintain that ein bishul aĥar bishul does not apply to liquids (see sections 5-6 above). But for those who maintain that ein bishul aĥar bishul applies to liquids as well, there is certainly no prohibition. This is the custom of Yemenite Jews. Ashkenazic custom maintains that as long as water is still warm, one may heat it to yad soledet bo. SSK 1:17 is lenient, and this is also the North African custom, as explained in YalkutShemesh §88.
At first glance, it would seem that if the pot is used for meat, there is a problem with placing it under the urn’s spigot to pour hot water into it, because steam will rise from the meat pot and the urn will absorb the meat flavor. Later, if the urn’s water is used to make coffee, this will constitute a transgression of the prohibition of mixing meat and milk. But the fact is that this meat-flavored steam is nullified by the much greater quantity of water in the urn (assuming that there is at least sixty times more water than the steam). In addition, this is a case where the reabsorbed flavor is twice removed from the original food and has not yet become part of a prohibited mixture (noten ta’am bar noten ta’am, or nat bar nat, de-heteira), and we are lenient in such cases. Furthermore, according to Baĥ and R. Akiva Eger, if the steam can dissipate into the air, the urn does not necessarily absorb the flavor even if it is directly above the pot. Nevertheless, in order to minimize contact between the steam and the urn, one should remove the pot’s cover for about ten seconds before moving it under the urn. One should also take care not to bring the pot too close to the urn. However, even if one did not take these precautions, the urn does not become a meat vessel as a result (see Harĥavot).
Earlier we learned about Bishul, which is prohibited by Torah law. Now we will examine two rabbinic enactments:
1) On Friday afternoon, one may not leave on the fire foods that are not yet cooked.
2) On Shabbat, one may not do things that resemble cooking.
We will begin by detailing the first enactment.
As a rule, the prohibitions relating to Shabbat begin when Shabbat begins. Therefore, by Torah law one may put a pot on the fire before Shabbat even though it will continue to cook on Shabbat. But the Sages were worried that one would be so anxious for his food to be properly cooked by Friday night that he would turn up the flame on Shabbat, thus transgressing the prohibitions of Mav’ir and Bishul. The Sages went even further and decreed that if one’s food needed more time to cook and he decided to leave it on the open fire, it may not be eaten on Shabbat.
In the past, cooking was done in a kira, a mini-oven that was heated by burning coals on its floor. The Sages were concerned that one would stoke the coals to accelerate the cooking process. Today, since we cook on gas flames, electric burners, or ovens, the equivalent concern is that someone will turn up the flame or raise the temperature, thus similarly transgressing the prohibitions of Mav’ir and Bishul.
Even if one were to leave the burners or oven on their highest temperature, rendering it impossible to turn up the fire, this is still forbidden; the Sages did not differentiate in this enactment. Furthermore, one might turn down the flame and raise it again later. Additionally, anytime one leaves uncooked food on an open fire, there is a concern that he will transgress Bishul in some way, such as by stirring the food or by covering it to preserve the heat.
There are two situations where there is no concern that one will raise the temperature, and, therefore, one may leave the food on the open fire or in the oven:
1) When the food is ready to eat, it can be left on the fire because there is no reason for anyone to raise the heat.
2) If the food is not yet fully cooked, it can be left on the fire if the fire is contained. In the time of the Sages, this meant that the coals had been cleared out of the oven (garuf) or covered with ash (katum) to lessen their heat. Today we accomplish this by covering the flame, which is why a plata may be used in this situation – its “flame” is naturally covered. In the upcoming sections we will continue explaining these two permitted cases.
. Har Tzvi, OĤ 1:136 and Yaskil Avdi, OĤ 7:28:8 permit leaving food that has not been adequately cooked on electric heat sources or in ovens if their heat cannot be raised. Or Le-Tziyon 2:17:3 permits leaving food on a flame that cannot be raised. R. Qafiĥ (commenting on MT 3:2, 12) even permits leaving it on a flame that can be raised, since such a flame does not sputter the way that coals do, so there is no concern that one will adjust it. Gidulei Tziyon 9:11 also allows leaving food on electric heat sources for this reason. This is quoted as the halakha by Tzitz Eliezer 7:16:3. However, the conventional ruling is that one may not leave food on an uncovered fire or electrical heating source. This is the approach of Igrot Moshe, OĤ 4:74, bishul 25; R. Shlomo Zalman Auerbach and R. Yosef Shalom Elyashiv, cited in Shvut Yitzĥak vol. 2 ch. 8; SSK 1:72; Yabi’a Omer 6:32; Hilkhot Shabbat Be-Shabbat 1:5:16. Be-di’avad if one followed those who are lenient, the food may be eaten (see MB 318:2).
One may leave food on an open fire on Friday afternoon if there would be no reason for anyone to raise the flame under the food. Poskim disagree what constitutes “no reason.” According to Rif and Rambam, if the food is fully cooked, and further cooking will be detrimental to it, then one may do so. But if additional cooking will improve the flavor of the food, then one may not leave it on the fire, since there is motivation to turn up the flame.
In contrast, the Ge’onim and Tosafot maintain that if the food has reached the point where it could be considered a ma’akhal ben Derusa’i, we are no longer concerned that one would desecrate Shabbat to turn up the flame. Only if the food is totally inedible are we worried that, due to concern that the food will not be ready for Friday night dinner, one might turn up the flame.
The bottom line is that one may leave food on an open flame if it can be eaten in a pinch, as this is the opinion of the majority of Rishonim as well as the custom of most Jewish communities. However, le-khatĥila one should take into account the stringent opinion and refrain from leaving food on an open fire if continued cooking will improve its flavor. This problem can be avoided by covering the flame, as we will now explain.
. Tanna’im disagree about this (Shabbat 36b). The majority of Sages maintain that only food that is fully cooked and that further cooking will damage may be left on an open fire. This is the ruling of Rif and Rambam. However, according to Ĥananya, one may leave food that has reached the state of ma’akhal ben Derusa’i on the fire as well. This is the ruling of the Ge’onim, Tosafot, and many Rishonim. SA 253:1 presents the stringent opinion as the primary one, and the lenient position as the secondary one. Rema, based on Rosh, writes that the custom is to be lenient even though le-khatĥila it is preferable to be stringent. BHL s.v. “ve-nahagu” reaches this conclusion as well. Some Sephardic communities are customarily lenient (Yalkut Yosef 253:1). Nowadays, since it is easy to cover the flame with a blekh, one can satisfy all opinions, as explained in the next paragraph. Ma’akhal ben Derusa’i is named for a robber who was on the run from the law, and became accustomed to making do with minimally cooked food so that he could eat quickly and then continue to flee. Rambam understood that this refers to half-cooked food, while Rashi maintains that it refers to food that is a third cooked. MB 253:38 states that in extenuating circumstances, one can be lenient once the food is a third cooked. (Although SA 254:1 explains that one may leave a pot with raw meat on an open flame because it cooks slowly, nowadays since we cook with gas whose flame is extremely hot, this is no longer permitted, as explained in Harĥavot.)It is important to note that the rabbinic rules pertaining to the concern that one will raise the flame relate specifically to cooking food; when using heaters or radiators to heat the house this is not an issue. (However, in the case of a wood-burning stove, one must make certain that the fire has indeed taken hold before Shabbat begins, as explained in SA §255.)
As we have learned, if food is not adequately cooked (whichever definition of “adequately,” as defined in the previous section, is adopted), one may not leave it on the fire before Shabbat begins, because one may come to turn up the flame on Shabbat. However, one may do so if the flame is covered. Covering the flame, thus reducing its heat, serves as a reminder not to raise the flame later. Furthermore, were one to forget and go to turn up the flame, he would see that the fire is covered and remember that this is forbidden, and thus refrain from proceeding. Therefore one may leave foods that are not adequately cooked on an electric plata, since its heating elements are covered.
One may also cover the fire by placing a blekh (metal sheet) over the burners and leaving adequately cooked foods on it, since covering the fire is a clear indication and reminder that it is Shabbat, effectively preventing one from forgetting and turning up the flame. Ideally, it is also recommended to cover the knobs that control the flames of the burners.
Although one may put foods on a blekh or plata even if they are not fully cooked, le-khatĥila it is better that all the foods be fully cooked before Shabbat begins. As long as they are not fully cooked, any action that will make them cook faster is prohibited by Torah law. For example, if one removed the cover on a pot containing food that is not fully cooked, one may not replace the cover. Similarly, one may not move the pot to a hotter place on the plata (as explained in section 3). Therefore, it is preferable to leave only fully cooked foods on a plata (SSK 1:72).
. In the times of the Sages, foods were cooked and heated in a stove that contained coals. The Sages decreed that if the coals were removed or covered with ash, it was permitted to leave food there even if it was not yet edible. Nowadays, since we do not cook on coals but rather on gas or electric burners, there is nothing truly similar to removing the coals. Nevertheless, the process of covering the fire with ash can be replicated simply by covering the flame. The purpose of covering the coals was to reduce their heat without putting them out entirely, so that one could still cook with them. The Sages were not worried that one would forget it was Shabbat and feed the fire, because the fact that the coals were covered would remind him that it was Shabbat and this is forbidden. Covering a gas flame with a blekh serves the same purpose; it reminds people that it is Shabbat, so there is no concern that they will raise the flame. Therefore, it is not necessary to cover the knobs on the stove. Indeed, SSK ch. 1 n. 218 (based on MB 253:14) states this, as do Or Le-Tziyon 2:17:2; Shvut Yitzĥak vol. 2, p. 21 in the name of R. Yosef Shalom Elyashiv; and R. Shlomo Zalman Auerbach as cited in Me’or Ha-Shabbat vol. 2, p. 628. This is also recorded by Igrot Moshe OĤ 1:93, which states the key is to cover the flame, even though le-khatĥila one should cover the knobs as well. Shevet Ha-Levi 3:49 maintains that the primary requirement is to cover the knobs in order to prevent the possibility of raising the flame, but requires covering the fire as well. Menuĥat Ahava 1:3:1 states that it is sufficient either to cover the fire or to cover the knobs. See n. 13 above, which mentions an even more lenient position, but we do not follow this.
If one wishes to leave food that is not fully cooked in an electric oven on Friday afternoon, he must do something to remind himself of Shabbat, to ensure that he will not turn up the heat on Shabbat. One option is to place a metal strip or thick aluminum foil between the pot or pan and the heating element. Since this reduces the heat reaching the food, he will remember that it is Shabbat and not raise the oven temperature. Alternatively, he may cover the oven knobs.
There is an additional problem with using an oven. If the oven has a thermostat, some maintain that one may not open the door of the oven because this may result in the heat cycling on (below 17: 8, and n. 8). In order to allow oven use according to all opinions, many ovens have a special setting for Shabbat. This setting bypasses the thermostat and guarantees that the oven maintains a constant low temperature unaffected by opening the oven door.
One may use an electric urn, but it is preferable to make sure the water boils before Shabbat. One should use an urn that does not have a thermostat. If it does have a thermostat, one should try to remove water only when the heating element is on (see below, ch. 17 n. 8). One may not use a device that automatically fills with cold water to replace the hot water that is removed, since that cold water is then cooked (section 24 below).
In principle, as long as one covers the oven knobs, he may leave raw food in the oven before Shabbat begins, and set a timer to turn on the oven an hour before the meal, so that the food will be ready in time. Similarly, one may put flour and water and other ingredients into a bread machine if its knobs are covered, and set the timer to turn on the machine, so that the bread will be kneaded and baked on Shabbat morning and finished in time for lunch. Indeed, some permit this in practice. Others prohibit it absolutely, fearing that it would lead to people actually cooking on Shabbat.
. In the time of the Mishna, ovens were very hot, and there was no permissible way to leave inadequately cooked food in them. Since a kira was not quite so hot, the Sages allowed it to be used on condition that the coals were either removed or covered (Shabbat 38b). The ovens that people have in their homes today, whether large or small, are not as hot as the ovens of old, so the laws of today’s ovens correspond to those of the kira (Rema 253:1; MB 253:28). However, the concern that one might “stoke the coals,” that is, raise the flame of the oven, still exists. To neutralize this concern, the Mishna suggests that one cover the coals with ashes in a way that will reduce their heat. In an electric oven, this is accomplished by placing a sheet of heavy foil or metal over the heating element, separating between it and the pot. This is the suggestion of Shvut Yitzĥak 2:7:3 in the name of R. Yosef Shalom Elyashiv. Az Nidberu 8:16 and Or Le-Tziyon 2:17:4 maintain that it is sufficient to place something between the bottom of the oven and the pot, and one may rely upon them (taking into account the lenient position presented above in n. 13). The second option is to cover the knobs. Even though this is not the same as covering the coals, nevertheless in practice it will remind people not to turn up the flame. (In our case one can more easily rely on covering the knobs, since in any case the fire is covered.) This also seems to be the opinion of Har Tzvi, OĤ 1:136; Yabi’a Omer 10:26:1; Shemesh U-magen 2:62; Menuĥat Ahava 1:3:7; and R. Yitzĥak Halperin. Orĥot Shabbat 2:15 permits using the oven if the knobs are taped in such a way that it is impossible to move them. We have already seen in n. 13 that some are even more lenient since we are not concerned that the fire will go out, but their opinion is not followed in practice.. The water must be boiled before Shabbat for two reasons. First, some say that an urn is considered an uncovered fire, and one may not leave water on an open fire to cook on Shabbat (SSK 1:46; Hilkhot Shabbat Be-Shabbat 1:5:26; Orĥot Shabbat 2:32). However, if it is impossible to raise the heat, then according to Minĥat Yitzĥak 5:91 and Shevet Ha-Levi 5:30 this is permitted. If one covers the knob that controls the heat, then many maintain that there is no problem of hashhaya, as explained above in n. 16. Even when one can turn up the heat, some are lenient, as mentioned in n. 13. Second, if one removes water from the urn before it is boiled up, he causes the remaining water to cook more quickly (Hilkhot Shabbat Be-Shabbat, loc. cit.; Orĥot Shabbat ch. 2 n. 39). If the urn’s spigot is at the very bottom, one may not use it. This is because when the water runs out, one might add cold water to prevent the heating element from burning out, as MB 318:68 mentions. Ĥut Shani 26:5 and Avnei Yashfeh 5:50 forbid using an urn even if the spigot is higher up, out of concern that the water might still get used up if one tilts the urn or if water evaporates on its own. But the rest of the poskim we mentioned do not feel it necessary to worry about this.
. Tzitz Eliezer 2:6 and Minĥat Yitzhak 4:26 forbid leaving fully cooked food on a plata before Shabbat when the plata has not yet turned on, because one may come to place food that is not fully cooked on the plata on Shabbat, and thus violate a Torah prohibition. In contrast, Melamed Le-ho’il §58 and SSK 1:32 permit placing fully cooked food on a plata before Shabbat if the plata is off; but they forbid putting on food that is not fully cooked, lest one place such food on the plata on Shabbat. Those who permit putting food that is not fully cooked on a plata that is off on Friday include R. Shlomo Zalman Auerbach (Minĥat Shlomo 2:34); Or Le-Tziyon 2:30:18; and R. Ovadia Yosef (Yabi’a Omer 10:26, where he mentions other Aĥaronim who rule similarly). The same law would apply to a bread machine as well. See Harĥavot.
Now that we have learned the laws of hashhaya, leaving food on a heat source before Shabbat, we will now explore the laws of hanaĥa: placing food on Shabbat somewhere that it will be warmed up. As we saw in section 3, the rule of thumb is that one may not cook on Shabbat, but one may reheat food due to the principle of ein bishul aĥar bishul. Therefore, one may remove fully cooked food from the refrigerator, such as cold chicken and kugel, and reheat them. The poskim disagree regarding reheating a liquid (as explained above in sections 5-6). However, the Sages prohibited reheating even cooked foods if one does so in a manner that resembles cooking, because he may forget that it is Shabbat and end up raising the flame and transgressing a Torah prohibition. Therefore, one may not reheat a fully cooked food over an open fire, since this is the way one normally cooks.
But one may reheat food if the method used is clearly not the normal way of cooking. Therefore, one may put a pot with cooked food on top of another pot, or on an urn that is on the fire, because this is not the normal way of cooking.
Poskim disagree, however, about placing food on a plata or a blekh.
According to many, one may not place even fully cooked food on these, because putting food on a heat source resembles cooking. However, if one places a pot or plate upside down on the plata or blekh, he may place food on them, because this is not a normal way to cook, as normally one would not place an obstruction between the heat source and the food. In practice, one may even rely upon a cover that lifts the food up only minimally (like the top from a metal coffee can) to serve as an obstruction between the plata and the food. However, aluminum foil, which does not lift the food up at all, is not acceptable. Those who are stringent maintain that one may not place even fully cooked food on an aluminum foil-covered plata or blekh.
In contrast, there are others who are lenient and maintain that since people do not normally cook upon a plata or a blekh but only over an open flame, when one places food on a blekh or plata it does not look like he is cooking, and therefore he may place cooked food directly on them on Shabbat. There are others who are lenient when it comes to a plata since it is especially designed for warming and not cooking, but are stringent regarding a blekh since it is hotter and can serve as a cooking surface.
In practice, since many poskim are stringent, it is preferable to be stringent and refrain from placing a pot with cooked food directly onto the plata or blekh. However, those who wish to be lenient may, since the law is rabbinic, and many important poskim have offered compelling reasoning in support of their lenient position. One who has a set family custom on the matter should follow his custom.
One may put fully cooked food on a heat source that is not normally used for cooking, such as a radiator, even if the radiator is very hot, since it does not resemble cooking (Igrot Moshe, OĤ 4:74, Bishul §34). Similarly, one may put fully cooked food on top of a kerosene or gas heater that is meant to heat the home as long as something separates the fire from the food and one does not warm up food or water there during the week. But if it is used during the week for heating food and water, then the laws pertaining to it are the same as those for a gas flame. Thus according to most poskim, one must put an upside-down pot on it, and only then may one reheat the food. Following the more lenient position, it is enough to put a blekh on the heater and place the food upon it.
. Included among the stringent are: R. Shlomo Zalman Auerbach (cited in SSK 1:30 and nn. 63 and 83); Or Le-Tziyon 2:17:1; Shevet Ha-Levi 1:91; and R. Meir Mazuz (cited in Menuĥat Ahava 2:10:28). In the same vein, Igrot Moshe, OĤ 1:93 is stringent about a blekh or plata that get so hot that one can cook on them; Kaf Ha-ĥayim 253:11 states similarly regarding a blekh. In their opinion, a plata is essentially a kira whose flame is covered. One may not put food directly on a plata, because even though the cover eliminates the concern that one will turn up the flame, there still remains the concern that it resembles cooking when one places things upon it. Ĥazon Ish 37:9, 11 is more stringent about leaving food on a plata or returning it to one, because, in its opinion, a plata is not considered covered since it itself is a heat source without a cover. This is also the opinion of R. Mordechai Eliyahu regarding a plata. SA 253:1 forbids leaving fully cooked food on the coals because of the prohibition of insulating; in R. Eliyahu’s opinion, when the bottom of a pot is resting on something that generates heat, this is considered insulating (hatmana) and is forbidden. In order to use a plata in a permitted fashion, one must put an additional metal piece on it that will create some space between the pot and the plata. (Or Le-Tziyon 2:17:1 rejects this reasoning, because SA was stringent only when speaking of a pot that was sinking into coals, but not regarding food that is placed on a flat and stable heat source.) R. Qafiĥ, in his commentary to MT 3:12, is stringent regarding returning pots to a plata or blekh, but not regarding leaving them on before Shabbat.Yeĥaveh Da’at 2:45, based on several Aĥaronim, takes a lenient position, as does Menuĥat Ahava 2:10:28. Tzitz Eliezer 8:26:5 inclines toward this and states that it is also the opinion of R. Frank. According to them, placing something on the plata does not resemble cooking, and the plata is comparable to a covered kira with an additional cover. Some are lenient only for a plata, where there is no concern of resembling cooking, because it is designed for reheating and not for cooking. Thus, the laws pertinent to a plata are not those of a kira but those of the sides of a bonfire, which were occasionally used to cook in the time of the Talmud (Igrot Moshe, OĤ 4:74, Bishul §35; R. Lior).
I wrote above that one who follows the stringent position may create an obstruction between the food and the plata or blekh by using an upside-down plate. This is suggested by SSK 1:44, n. 126, based on MB 253:81. (In contrast, Ĥazon Ish maintains that one may place food on the plata or blekh only if he places it on top of a pot with food in it; however, one may not put it on an empty pot that is on the plata, because that would be like stacking one blekh on another over the fire – it does not help, because it still looks like cooking.) It would seem that using the metal cover of a coffee can does not look like cooking, and moreover one may take into account the lenient position.
Sometimes one removes a pot from the plata on Shabbat in order to remove food, and then wishes to return it to the plata. May one take this action, known as haĥzara? Once again there is disagreement among the poskim.
According to those who are lenient and allow placing food on a plata or blekh on Shabbat (maintaining that this does not resemble cooking, as explained in the previous section), one may certainly return a pot to the plata if it had already been there on Shabbat, as long as the food is fully cooked and the fire is covered. (If the food is not fully cooked, one violates the Torah prohibition of cooking. As long as the fire is covered, there is no concern that he will turn up the flame.)
Those who are concerned that placing cooked foods on the plata on Shabbat resembles cooking, and thus forbid doing so, view returning food to the plata differently. Since the food was already on the plata before Shabbat, returning it does not resemble cooking. Therefore, as long as it is clear that one is simply returning the pot to the plata, and not placing it there for the first time on Shabbat, he may do so. In order to make it clear that this is haĥzara and not initial placement, three conditions must be met, le-khatĥila: 1) the pot must not be placed on the floor; 2) the person removing it must have in mind that he will return the pot to the plata; 3) the person must keep hold of the pot until he returns it to the plata. Be-di’avad, if there is a great need to return the pot to the plata because that is the only way there will be hot food at the meal, then even if these three conditions are not met, one may return the food to the plata. This is because the food is still, in fact, being returned to the plata, and not being placed there for the first time.
. The laws of haĥzara apply specifically to a kira, and the leniency is on condition that when one returns the pot, he places it on top of the kira and not inside it. (If he wishes to place food there on Shabbat, there must be some additional separation between the kira and the pot.) For those who maintain that placing a pot on the plata is forbidden because it resembles cooking, haĥzara may still be permitted, since this would be the equivalent of placing an item on a kira and not inside it. However, one must ensure that certain conditions are met. SA 253:2 mentions only the first condition, that the pot is not placed on the ground. Some maintain that placing the pot on the counter is the equivalent of putting it on the ground, since the counter is attached to the ground (Or Le-Tziyon 2:17:6; Menuĥat Ahava 1:3:5). Others maintain that the counter is different from the ground, because it is normal to briefly place a pot on the counter and then return it to the stove (Az Nidberu 8:17). The custom is to be lenient. One who wishes to be stringent should place the pot on a towel instead of directly on the counter (see SSK, ch. 1 n. 61).Two additional conditions are mentioned by Rema. If one places the pot on a bench, according to Rema, as long as he keeps hold of the pot he may replace it. But if he places it on the ground, it does not help to keep hold of it; he must hold it so that only part is on the ground and part remains in the air (Shvut Yitzĥak vol. 2, p. 161, based on Maharam Schick §117). According to Igrot Moshe, OĤ 4:74, Bishul §33, if one keeps hold of the pot, that is enough to render haĥzara permissible, even if it was placed on the ground. In any case, be-di’avad if one did not meet this condition, Rema is more lenient. According to SA, the first condition is absolute; if one placed the pot on the ground, he may not return it. According to Rema, however, be-di’avad he may return it even if it was placed on the ground. I did not record SA’s opinion in the main text because some maintain that it is always permitted to heat cooked food on a plata or blekh. Therefore, even those who are stringent can be lenient here and follow Rema. All of this of course assumes that there is no problem of actually cooking when one returns the pot to the heat source. Regarding liquids, see sections 5-6 above. According to SA, one may return liquids to the plata only if they have not cooled to below yad soledet bo, while according to Rema 318:16, as long as they retain some warmth this is permitted. However, some are more stringent and maintain that one may not return a pot to the plata itself because a plata is considered the equivalent of a kira whose coals have not been covered. This is the opinion of Ĥazon Ish, OĤ 37:9, 10 and R. Qafiĥ. However, since this law is rabbinic and the vast majority of poskim are lenient, I did not present this opinion in the main text.
As we learned in the previous section, if food was placed on a plata before Shabbat, even those who are stringent permit removing this food from the plata and replacing it. Therefore, if food was placed on the periphery of the plata before Shabbat, one may move it to the center to allow it to heat more effectively on Shabbat, since it was already on the plata and this is not considered a new placement. Of course, this only applies to food that is fully cooked. If the food is not fully cooked, any action that raises the temperature of the food will cook it, and is thus prohibited by Torah law.
Similarly, one who uses two platas may move a pot from one to the other on Shabbat, as long as the food in the pot is fully cooked and still hot. If one placed a pot of fully cooked food on a blekh before Shabbat, and the fire underneath it goes out on Shabbat, he may move the pot to a second blekh or plata. As long as the food is still hot, it is clear that it was on the plata before Shabbat, and moving it to a different plata is thus considered haĥzara and not initial placement.
When one wishes to heat numerous foods for Shabbat, one may place two layers of pots on the plata. Friday night’s food may be placed in the lower level of pots and removed when needed for the meal. The pots that were on top of them may then be placed on the plata, as long as the food in them is fully cooked. This is not considered a new placement as long as they are yad soledet bo and the person’s intention was always to place them directly on the plata once there was room to do so.
If one wishes to warm up fully cooked food, and there is an open fire, one may cover the fire with a blekh, set a plate on it (following the position of most poskim, quoted above in section 18), and place the food upon the plate. Even if this covering changes the shape of the flame, it is not prohibited since the strength of the fire remains unaffected (SSK ch. 1 n. 66).
. Some are stringent, however, maintaining that since the fire underneath it went out, it is as if the pot is resting on the ground. Thus, if one wishes to move it to a different plata, it is considered a new placement, and is prohibited unless he places an overturned plate underneath the pot. This is the opinion of SSK 1:27. However, n. 79 there cites R. Shlomo Zalman Auerbach’s rationale for leniency. Igrot Moshe takes the latter approach as well in OĤ 4:74, Bishul §38, and this is also the opinion of R. Shmuel Wosner and R. Yosef Shalom Elyashiv as cited in Otzrot Shabbat 70:89-90. This whole discussion is only relevant for the stringent approach, which does not allow placing cold food on the plata, as explained in section 18 and n. 19. But for those who are lenient and maintain that one may put fully cooked cold food on a plata (Yeĥaveh Da’at and Igrot Moshe), one may certainly be lenient in this case.. However, some are stringent and maintain that since the pots on the top level were not resting on the plata, moving them directly to the plata would be considered a new placement, which is forbidden according to the stringent opinion described in section 18. This is the approach of SSK 1:44, Ĥazon Ish 37:11, and Shevet Ha-Levi 1:91. (Ĥazon Ish also maintains that one may not place these pots on top of an empty pot, as explained in Az Nidberu 3:14.) In SSK n. 125 is mentioned the rationale of R. Shlomo Zalman Auerbach to be lenient and rely on the position of Ran. Since we saw in section 18 that some maintain that le-khatĥila one may place fully cooked cold food on the plata, in this case even those who are usually stringent may be lenient le-khatĥila.
There is another case where the poskim disagree about haĥzara: If there is a large pot on a plata or blekh whose heat source is covered, may one pour its contents into a smaller pot, and then place the smaller pot on the plata? According to MA 253:20 this is forbidden, while according to SHT 253:47 this is permitted. Therefore SSK ch. 1 n. 49 and Brit Olam, dinei hashhaya ve-hatmana §17, state that le-khatĥila one should be stringent, but if necessary one may be lenient. It seems reasonable to be lenient in this case even le-khatĥila, since we can also invoke the opinion allowing one to place things on the platale-khatĥila (see section 18 above). Regarding liquids, as explained in n. 12, some maintain that according to SA 253:4 it is forbidden because of the possible prohibition of cooking. But Rema and other poskim maintain that even according to SA, in times of necessity it is permitted.
If a pot containing food was in a hot oven, and the pot was removed from the oven so that food could be removed from it, it may not be returned to the oven. There are two reasons for this. First, since there is nothing reducing the temperature of the oven, there is a concern that when one returns food to the oven, he will forget that it is Shabbat, and turn up the temperature. Second, this action resembles cooking. One possible solution to both these problems is to place the food within a four-sided metal box inside the oven. In such a situation we are not worried that one will raise the oven’s temperature, nor does it resemble cooking when he returns the food to it, since normally people do not cook food in a box. It would seem that one may also be lenient if one puts a pan or overturned plate on the bottom of the oven, and then inserts the food. Additionally, one should cover the oven knobs.
In order to return food to an oven, one must meet the conditions necessary to permit haĥzara outlined above (section 19). In other words, since food was in the oven, and the person taking it out intended to return it, this does not resemble cooking. However, one may not place cold food in a hot oven, since that does resemble cooking.
If the oven is controlled by a timer, one may place fully cooked food in the cold oven, so that it will heat when the oven goes on. This does not resemble cooking, since the oven is off. In order to avoid the concern that one might raise the temperature, the knobs must be covered or the food must be placed on an upside-down pan. However, some poskim forbid this because they maintain that even though the oven is off, putting food in it to heat resembles cooking. However, in practice, since the law is rabbinic, one may rely on the lenient opinion.
Some people have a plata with a compartment that is set up on top of it, into which pots can be placed. Food that was removed from such a plata may be returned to the compartment. This does not resemble cooking because no one cooks in such a compartment, and its sole purpose is to keep foods on the plata warm (SSK 1:79). Those who place fully cooked cold food on the plata (as explained in section 18) may put food on this kind of plata as well. Those who are stringent may place the food on an inverted plate. Placing things into the compartment is not considered hatmana (see below), because the prohibition of hatmana is relevant only when the pot is in full contact with what surrounds it, while in this case not all the sides of the pot touch the compartment.
. One may not return a cooked food to the oven for two reasons: lest he stoke the coals (increase the flame), and because it resembles cooking. So state SSK 1:19 and Minĥat Yitzĥak 3:28. However, if one places a box inside the oven and replaces the food inside the box, according to Igrot Moshe OĤ 4:74, Bishul 27, it is permitted, because once one takes action to minimize the heat, there is no fear that he will forget about Shabbat and increase the heat. It also no longer resembles cooking. Hilkhot Shabbat Be-Shabbat 1:5:25, p. 237 states similarly in the name of R. Elyashiv. Shabbat Ke-halakha 1:9:36 permits if one returns the food on top of an inverted pan, thereby minimizing the heat (the equivalent of covering the coals) and demonstrating that he is not cooking. According to AHS 253:17, nowadays there is never a concern that returning food to an oven resembles cooking. Earlier sources explain that people used to cook in an oven and heat food on top of it. Therefore, when anyone placed food into an oven, it resembled cooking. But today’s ovens are built in such a way that one cannot heat food on top of them, and thus even heating food (without cooking) is accomplished by placing food inside the oven. Therefore, putting food in the oven does not necessarily indicate that one is cooking. Shevet Ha-Levi 3:48 and Menuĥat Ahava 1:3:8 state this as well. Nevertheless, it is still necessary to take some action that corresponds to covering the coals to remind people not to turn up the flame. According to Shevet Ha-Levi, one does this by placing a pan as a barrier between the heating element at the bottom of the oven and the food, while according to Menuĥat Ahava this can be accomplished by covering the knobs. Yalkut Yosef 253:8 permits returning the food even without an upside-down pan or covered knobs, because in its opinion, heating elements that are not visible are considered covered, and there is no concern that one will adjust the flame. All this is on the condition that one meets the requirements necessary to permit haĥzara.. R. Levi Yitzhak Halperin, in his book Kashrut Ve-Shabbat Ba-mitbaĥ Ha-moderni, permits this because when the oven is off, placing food inside it does not resemble cooking. In order to prevent the possibility of raising the temperature, the knobs should be covered or removed. It is also preferable le-khatĥila to set the oven at a temperature lower than is generally used for cooking. This is cited in Peninei Hora’ah, p. 113 and is the ruling of R. Lior. Yabi’a Omer 10:26 is even more lenient, in a sense. Ĥazon Ish 38:2 prohibits this, as do Minĥat Yitzĥak 4:26:10; SSK 1:32; Orĥot Shabbat 2:68; Hilkhot Shabbat Be-Shabbat vol. 1, p. 251; and Shvut Yitzĥak 2:9:1-2. Also see Harĥavot on section 17.
Because lighting a fire on Shabbat is prohibited, it is difficult to keep food warm. Nowadays we have electric platas that solve this problem, but in the times of the Sages this was a great challenge. One way to accomplish this was to place the pot of cooked food in the oven (as explained above in sections 14-16). Another way was through hatmana (insulation): enveloping the pot in wool or a different material to preserve its heat.
However, there are two rabbinic prohibitions that limit hatmana. The first applies before Shabbat, and the second on Shabbat itself. The first prohibition is that one may not insulate using a material that itself generates heat, such as hay or olive dregs. This prohibition goes into effect even before Shabbat begins, as the Sages were worried that if people insulated foods on Friday using these materials, they might mistakenly conclude that it was permissible to insulate foods on Friday using coals, and they would end up stoking the coals. Therefore, the Sages forbade insulating foods before Shabbat using heat-generating materials. However, one may insulate food using materials that do not generate heat, such as clothing, towels, blankets, and the like, as long as one does this before Shabbat.
The second rabbinic prohibition is that one may not insulate warm food on Shabbat itself, even when the material used does not generate additional heat. This is due to the concern that if insulating on Shabbat were permitted, some people would first heat the food on the fire and then insulate it, thus violating the prohibitions of Mav’ir and Bishul (SA 257:1-3).
One may fill a thermos with hot water on Shabbat, because placing something hot into a utensil is not considered hatmana. Similarly, one may place a bag of rice or other cooked foods in a cholent pot while keeping it separate from the cholent, because hatmana does not apply to insulating one food within another.
. This is the opinion of R. Shlomo Zalman Auerbach (SSK ch. 42 n. 242); Or Le-Tziyon 2:18:3; and R. Ovadia Yosef (Halikhot Olam 4, Parshat Bo 13). In contrast, SSK 42:63; Menuĥat Ahava 1:3:27; and Shevet Ha-Levi 3:47 are stringent. Nevertheless, the rationale of those who are lenient is convincing, and when in doubt about a rabbinic rule we are lenient. There is another reason to be lenient regarding filling a thermos with hot water: the prohibition of hatmana does not apply to a kli sheni (SSK 1:83).
One may not wrap pots on the plata in towels or blankets even before Shabbat. Although the towels or blanket do not generate heat, nevertheless since the pot is on the plata and the plata generates heat, this is considered insulating with something that generates heat, which is forbidden even before Shabbat.
The prohibition of hatmana applies only when the pot is wrapped on all sides, but if it is not surrounded there is no prohibition. Therefore, one may wrap most of the pot on the plata with a towel or blanket, because as long as the pot is not entirely covered, there is no prohibition of hatmana. One may do this even on Shabbat (Rema). Similarly, one may place a pan on top of a pot and drape a towel over the pan; as long as the towel does not touch the sides of the pot, it is not considered hatmana (SA 257:8). One must take care not to place a damp towel on the pot, because drying using heat transgresses the prohibition of laundering (below 13:3).
Some prohibit using a slow cooker (a pot made of ceramic or porcelain, surrounded by a metal housing that contains a heating element (“Crock-Pot”) because of hatmana, since the pot is surrounded by the heating element. If the food inside is uncooked, they maintain that there is an additional prohibition, as this constitutes leaving a pot on an uncovered fire. In contrast, others feel there is no prohibition of hatmana in this case, since the top of the pot is visible. In order to avoid the issue of hashhaya, if the food is not fully cooked, one must cover the knobs that control the temperature. This is the halakha in practice.
. SA 253:1; 257:8 lists two stringencies pertaining to hatmana:1) If an item that does not generate additional heat, such as an item of clothing, is resting on something that generates heat, like a plata, this is considered insulating with a heat-generating item.
2) Insulating with an item that generates heat is prohibited even if the pot is only partially covered (as in the case of insulating with coals). Therefore, according to this opinion, one may not cover a pot that is on the plata with a towel even if the cover is only on top or on one side, and even if it is placed there before Shabbat, since this is considered insulating with a heat-generating item. This is also the opinion of Menuĥat Ahava 1:3:19-20.
In contrast, Yabi’a Omer 6:33 is lenient and allows one to fully wrap a pot on the plata with blankets before Shabbat. This is because according to Ramban, as long as there is space between the heat source and the pot, it is not considered insulating with a heat-generating source. In R. Ovadia’s opinion, since there is space between the plata’s heating element and the metal sheet that comes into contact with the bottom of the pot, there is no hatmana here. This is also the opinion of R. Messas (Shemesh U-magen, OĤ 3:50).
Rema has an intermediate position. If there is a heat source below the pot, even if the covers above do not generate heat, they are considered as if they do generate heat. However, if the pot is not surrounded on all sides, it is permitted; the prohibition of hatmana applies only if the pot is completely wrapped. This is the practice of Ashkenazim, as recorded in SSK 1:77. Or Le-Tziyon 2:17:10 is lenient in accordance with the Sephardic custom and Yabi’a Omer, but adds that it is preferable not to cover the pot entirely (like the Ashkenazic custom) and that when possible, it is preferable to be stringent like SA. In the main text I follow Rema’s intermediate position.
. Those who do not allow slow cookers to be used on Shabbat maintain that if most of the pot is surrounded, and certainly when all of the pot is surrounded and only the top is not, it is still considered hatmana with heat-generating material. Therefore one may not use a slow cooker on Shabbat, even if it is activated on Friday afternoon. This is the opinion of R. Shlomo Zalman Auerbach (Minĥat Shlomo 2:34:5) and Orĥot Shabbat ch. 2 n. 149, in the name of R. Yosef Shalom Elyashiv. According to them, a slow cooker could only be used if one inserts something to lift the pot and distance it from the heating element. There is also the problem of hashhaya. Since slow cookers have temperature controls, there is a concern that one might turn up the temperature. To avoid this problem, one must either cover the heating element to lessen the heat or make sure that the food is already completely cooked when Shabbat begins. Those who are permissive feel that since the pot is not entirely covered, it is not considered hatmana (based on Rema 253:1 and MB ad loc. 48). If the food is not fully cooked, one should cover the knobs (see section 17 above). This is also the opinion of R. Ovadia Yosef in Ĥazon Ovadia, Shabbat vol. 1, p. 64 and Shevet Ha-Levi 9:52. Since this is a rabbinic law, the halakha follows those who are lenient. Additionally, the lenient position is compelling. See Harĥavot.
One may not benefit from water that was heated in a forbidden fashion on Shabbat. But if the water was heated in a permissible fashion, one may benefit from it on Shabbat. Seemingly, then, if a boiler was on before Shabbat, one could use the hot water produced by it even on Shabbat. However, there is a problem. Today’s electric boilers are built in such a way that whenever the hot water is turned on, cold water flows into the boiler tank to replace it. If the heating elements in the boiler are working and heating, then turning on the hot water tap on Shabbat causes cold water to enter the boiler and become cooked. Therefore one may not turn on the hot water on Shabbat when the boiler is on.
If the electric boiler was turned off before Shabbat, then the question whether the hot water may be used depends on whether the cold water that will flow into the boiler will become cooked. If the hot water coming out is scalding, it would be forbidden to turn on the hot water tap, because the replacement cold water would become cooked. But if the hot water is cool enough to touch, even just barely, then even if it is yad soledet bo it can be used on Shabbat, because the remaining water in the boiler cannot cook the incoming cold water (as explained in the note). When it is unclear whether the hot water is hot enough to cook the incoming water, one may turn on the faucet, as this is only forbidden if it is clear that the cold water entering the boiler will become cooked. If it is initially unclear how hot the water is, but when the faucet is turned on it becomes clear that it is extremely hot, cold water should be added to reduce the water’s temperature to below yad soledet bo.
One may also set the electric boiler on a timer that will turn it on for 15 minutes every few hours. This way, the water will heat somewhat, but will not reach yad soledet bo. One can then use the lukewarm water on Shabbat without worrying.
. Although some maintain that yad soledet bo is the temperature at which it is unpleasant to touch something for an extended period of time, a temperature of approximately 45°C (see section 4 above), in this case one only needs to be stringent when the water coming out of the boiler is over 80°C and cannot be touched at all. This is because our boilers are built in such a way that the hottest water is at the top of the boiler while the water at the bottom is not as hot. (The cold water enters the boiler through the lower part.) There is a significant difference between their temperatures. If one is able to touch the hot water that comes out of the top part of the boiler, it is almost certain that the water at the bottom of the boiler is not yad soledet bo, and certainly is not capable of cooking the cold water that will enter the boiler.When in doubt, one may turn on the hot water tap and check if the water is yad soledet bo. Even if it turns out that the water is burning hot, this is not prohibited. This is because when he turned on the water there was a doubt, and this is a case of davar she-eino mitkaven. This is certainly the case according to Taz, and perhaps also according to R. Akiva Eger, because one might use so much water that the remaining water will not be able to cook anything (see above 9:2 and Harĥavot here). In addition, the flow of cold water into the boiler is caused indirectly, and without the intention to heat it (see SSK ch. 1 n. 132). One may even use the water without being considered benefiting from a melakha. Since one did not know if the water is burning hot, it was permissible for him to turn on the hot water tap. Once the burning hot water is already flowing, one may add a great deal of cold water to it so that it will no longer be yad soledet bo (because if it is yad soledet bo, then the cold water that is being added to the burning water will cook). Once the hot water is released, it is preferable to wash as many dishes as possible, so that the hot water will come out of the boiler and the remaining water in the boiler will be unable to heat the cold water flowing in. If one needs only a little hot water, some say that it is still forbidden to turn off the hot water tap until all the hot water comes out. This is to make sure that the cold water flowing in will not cook (Menuĥat Ahava 2:10:13). Others permit the tap to be closed, because the cooking is done via grama, and we are not stringent when a loss is involved (Otzrot Shabbat ch. 1, p. 61 in the name of Shevet Ha-Levi; see SSK 1, the end of n. 131). The halakha follows those who are lenient. This is because in addition to their reasoning, it is almost always still doubtful whether the water remaining in the boiler would in fact be able to cook the incoming water; even if it could, it would be a davar she-eino mitkaven, which makes the prohibition rabbinic; additionally, the action is performed via grama.
It would seem that the following applies in a time of need, such as a cold day when it is difficult to wash the dishes using cold water, and one needs to wash a large number of dishes and use a large quantity of hot water. Even if it is clear that the water in the boiler is very hot, he may still use it, by first opening the cold water tap and then the hot water tap. This way, the cold water coming into contact with the hot water will not cook. Since it is clear that one will use a lot of hot water, it is also clear that the remaining water in the boiler will not be able to cook the cold water that will flow in as a result.
The Torah prohibition of cooking refers to cooking using the heat of a fire (esh) or using something that was itself heated by fire (toldot ha-esh). In contrast, one may cook using the heat of the sun (ĥama). Therefore, one may leave an egg in a place where the sun is beating down hard enough to cook it. However, it is rabbinically prohibited to cook using something that was itself heated up by the sun (toldot ha-ĥama). This is due to the concern that if one cooks in such a pan, he may mistakenly come to cook in a pan heated by fire, and will thus transgress a Torah prohibition (SA 318:3; MB 17).
In practice, then, one may only cook in the heat of the sun itself, but cooking using toldot ha-ĥama is rabbinically forbidden. Thus the question of a solar boiler (“dud shemesh”) is dependent on how we categorize it. Is the water in a solar boiler considered heated by the sun itself, or by toldot ha-ĥama?
According to several poskim, one may not use water that comes from a solar boiler, because the water is heated up with the help of receptors and black pipes, which are toldot ha-ĥama, and removing water from its tank causes the cold water that enters it to cook (Minĥat Yitzĥak 4:44; Az Nidberu 1:34). Another reason to prohibit this is that since many solar-powered boilers have the option of being powered by electricity by flipping a simple switch, there is a concern that if people use solar-heated water, they might also come to use electrically heated water. Therefore, it is better to avoid using hot water from the solar boiler (SSK 1:51 in the name of R. Shlomo Zalman Auerbach).
Others maintain that one may use hot water from the solar heater, because it is considered heated by the sun itself. The receptors simply help to focus the sunlight and aid in its absorption. If so, there is no problem of cold water flowing into the boiler as hot water flows out, because one may cook this water on Shabbat in the sun’s rays (Har Zvi, OĤ 188; Tzitz Eliezer 7:19; R. Qafiĥ; Yabi’a Omer 4:34; Or Le-Tziyon 2:30:2).
In practice, since this disagreement is on a rabbinic level and we are generally lenient in such disputes, one may be lenient and use hot water from a solar boiler on Shabbat. Those who wish to be stringent should be commended. However, when it comes to bathing babies, one should not be stringent.
Today there is an additional type of boiler, mainly used in very tall buildings. In this boiler, the hot water in the receptors remains in a closed system of pipes that descend to the water tank, and the cold water is heated upon contact with these pipes. Thus, the cold water is heated via toldot ha-ĥama. Hot water from this kind of boiler may not be used on Shabbat, because turning on the hot water tap causes the cold water flowing in to become cooked by toldot ha-ĥama. But on Friday night one may use hot water that was heated before Shabbat, as explained in the note.
. One does not need to take into account that the cold water that will flow into the boiler will be heated by contact with the hot water that was heated through toldot ha-ĥama, because there is no certainty that the water entering the boiler will be heated to yad soledet bo. The incoming cold water can only be heated in this way if the tank is completely filled with very hot water. But if the water at the bottom of the tank is still not very hot, it will not have the ability to heat the cold water; it will only be heated up by the receptors, i.e., directly by the sun. When one is in doubt about how the cold water will be heated, it is a davar she-eino mitkaven. And even when it is certain, there is room to be lenient since this case is a psik reisha de-lo niĥa lei in the case of a double rabbinic prohibition, for which we are lenient. The two rabbinic factors are: 1) cooking using toldot ha-ĥama is a rabbinic prohibition, and 2) the entry of the cold water is done via grama. (See Harĥavot here, 24:2 and 25:1.) The unintentional result here is undesired, because it would be better for the person if the water is heated by the receptors rather than by the water in the tank; the latter case would cool down the hot water in the tank.. In a normal system, when one turns on the hot water tap, first all of the cold water in the pipe that descends from the tank on the roof comes out of the faucet. In contrast, in this new system, the hot water stays in the apartment’s tank and reaches the faucet immediately, saving time and water. Additionally, less scale accumulates in it. However, since the cold water is heated by the pipes that pass through the tank, it is cooked through toldot ha-ĥama, which is rabbinically prohibited. One cannot maintain that this is a psik reisha de-lo niĥa lei in a rabbinic prohibition, because it is to his advantage for the cold water to enter the tank and heat up. On the other hand, on Friday night it is not to his advantage for cold water to enter the tank, because it will cool down the tank’s hot water; and since there is no sun then to heat the water flowing through the pipes, the water in the tank will remain cold through the night. Therefore, on Friday night one may use the hot water from the tank. However, during the day it is beneficial to him for the cold water to enter the tank, because the sun will quickly heat the water in the pipes descending from the receptors on the roof. In a case of necessity, it may be that even during the day one may use the hot water, because of the combination of two rationales: 1) Perhaps we can consider the action grama (see Har Tzvi §188; Tzitz Eliezer 7:19). 2) According to a minority of poskim, psik reisha is not forbidden if the prohibition involved is rabbinic (above 9:2 and Harĥavot 9:5:4).