02 – Principles of the Prohibition of Ḥametz

01. Four Mitzvot Concerning the Prohibition against Ḥametz

Four Torah commandments deal with the prohibition against ḥametz on Pesaḥ: three negative and one positive.

The first prohibition is to refrain from eating ḥametz, as it is written, “And ḥametz shall not be eaten” (Shemot 13:3). Our Sages taught that the prohibition against eating ḥametz on Pesaḥ includes not deriving any kind of benefit from the ḥametz. The Torah further states: “You shall not eat any leavened product (maḥmetzet)” (Shemot 12:20). Our Sages concluded from this verse that not only something that had fermented on its own is prohibited, but even food that had been leavened by some external agent may not be eaten on Pesaḥ. It must be noted that the Torah was particularly stringent concerning the prohibition against eating ḥametz. Almost all of the Torah’s food prohibitions are punishable by lashes, while eating ḥametz on Pesaḥ is punishable by karet (extirpation), as it is written, “whoever eats ḥametz from the first day until the seventh day, that soul shall be cut off from Israel” (Shemot 12:15).

The second prohibition is that no ḥametz may be found in our possession, as it is written, “Seven days there shall be no se’or found in your homes” (Shemot 12:19). Se’or is the “starter” or leavening agent used to make dough ferment. This verse means not only that se’or is forbidden, but also that no ḥametz may be found in our possession. This prohibition is often called bal yimatzei.

The third prohibition is that no ḥametz may be seen in our possession, as it is written: “Matzot shall be eaten seven days; and no ḥametz of yours shall be seen, and no se’or of yours shall be seen within all your borders” (Shemot 13:7). One violates the second prohibition (bal yimatzei) and this third prohibition (called bal yera’eh) only if one has in his possession on Pesaḥ at least one olive’s bulk (kezayit) of ḥametz. If the volume of the ḥametz that remained in one’s possession was less than a kezayit, he does not violate bal yera’eh and bal yimatzei on account of that ḥametz.

The fourth mitzva – a positive commandment – is to eliminate ḥametz and se’or in advance of Pesaḥ, as it is written, “Seven days you shall eat matzot; however, on the first day you shall remove the se’or from your houses” (Shemot 12:15).

02. When Ḥametz Is Prohibited by Torah Law and by Rabbinic Law

Although the prohibition against ḥametz applies primarily during the seven days of Ḥag Ha-matzot (from the 15th through the 21st of Nisan), we are nevertheless commanded to remove ḥametz from our homes by midday of the 14th of Nisan, Erev Pesaḥ.

The prohibition against eating ḥametz also begins at midday on the 14th, as it is written, “And you shall sacrifice the Pesaḥ [offering] to God…you shall not eat ḥametz with it” (Devarim 16:2-3). This prohibits the eating of ḥametz from the time fit for bringing the Pesaḥ sacrifice, i.e., at midday on the 14th of Nisan. This prohibition against eating ḥametz includes the prohibition against deriving any benefit from it.[1]

In order to distance one further from possibly violating commandments, the Sages added to the prohibitions and forbade gaining benefit from ḥametz for an additional hour. They also forbade eating ḥametz for two extra hours, since on a cloudy day (and where there are no clocks) people are likely to err by as much as two hours.

These times are calculated by dividing the day into twelve equal parts, each of which is called “a seasonal hour” (“sha’ah zemanit”). Thus, one may eat ḥametz for the first four seasonal hours of the 14th. During the fifth hour it is rabbinically forbidden to eat ḥametz, but it is permissible to derive benefit from it by, for example, feeding it to an animal or selling it to a gentile. With the onset of the sixth hour of the day, it becomes forbidden rabbinically to derive benefit from ḥametz, and if one forgot to sell it to a gentile by then, it must be destroyed. When midday arrives, that is, after the sixth hour ends, ḥametz is forbidden by Torah law both for consumption and for deriving any benefit, and one must dispose of it as soon as possible. Every moment that one does not get rid of it, he violates the positive commandment to eliminate ḥametz (see below, 3:6).

Once the holiday begins, two additional prohibitions apply: bal yera’eh and bal yimatzei.[2] The prohibition against eating ḥametz also becomes more severe: one who willfully eats ḥametz after midday on the 14th is punishable by lashes only, whereas one who willfully eats ḥametz after the holiday begins is punishable by karet. This is based on the verse: “whoever eats ḥametz, from the first day until the seventh day, that soul shall be cut off from Israel” (Shemot 12:15).

Ḥametz becomes permissible once again after Pesaḥ, except that our Sages forbade ḥametz that belonged to a Jew during the holiday (“ḥametz she-avar alav ha-Pesaḥ”). Since by keeping the ḥametz on Pesaḥ he violated the prohibitions of bal yera’eh and bal yimatzei, the Sages prohibited eating or gaining benefit from that ḥametz even after Pesaḥ. Ḥametz that was in the possession of a gentile during Pesaḥ, however, is permissible; a Jew may buy it and eat it (SA 448:1-3).


[1]. The mitzva of removing the ḥametz applies from midday on the 14th, as it is written, “However, on the first day you shall remove the se’or from your houses” (Shemot 12:15). The Sages deduced from other verses that “the first day” refers to Erev Pesaḥ. Since the ḥametz must already have been removed by the onset of the holiday itself so as not to violate bal yera’eh and bal yimatzei, the mitzva of removing the ḥametz must be in the middle of the day preceding Pesaḥ, that is, at midday (Pesaḥim 4b).

The prohibition against eating ḥametz and obtaining any benefit from it applies from midday on the 14th according to R. Yehuda, as explained in Pesaḥim 28a. Rambam, as well as R. Yitzḥak ibn Gi’at, Rosh, and most Rishonim, ruled in accordance with this view. R. Shimon’s view is that the prohibition against eating ḥametz begins with the holiday itself, and it is only the mitzva of removing the ḥametz that comes into effect at midday on the 14th. Some Rishonim rule in accordance with this view, although they disagreed about what the mitzva of eliminating ḥametz entails according to R. Shimon. According to Ramban and Raavad, since one is obligated to eliminate the ḥametz, it is also forbidden to eat it; yet Torah law permits him to benefit from it in the course of its being burned. Only the Sages prohibited deriving any benefit from the ḥametz from the beginning of the sixth hour of the day. According to Ha-ma’or, the mitzva of disposing of the ḥametz does not imply a prohibition against eating it, since by eating it, one is, in fact, disposing of it. As noted, the view of most poskim is that the halakha follows R. Yehuda’s view that the prohibition against eating ḥametz and the prohibition against deriving any benefit from ḥametz are of Torah origin and apply from midday. This is how the halakha is decided in SA (443:1).

According to R. Yehuda, ḥametz she-avar alav ha-Pesaḥ is forbidden by the Torah, whereas according to R. Shimon, the Torah permits it, but the Sages decreed it to be forbidden (Pesaḥim 28b-29a). The halakha follows the latter view (MT, Laws of Ḥametz and Matza 1:4; MB 448:7).

[2]. This is because, with respect to these prohibitions, the Torah states “seven days” explicitly (Raavad, Maharam of Rothenburg, MA, MB 443:1. Others say that the prohibition starts on midday of the 14th (Rashi, and this is also implied by Rabbeinu Ḥananel and Itur, SHT 443:2).

03. What Is Ḥametz and What Is Se’or?

The ḥametz that is prohibited by the Torah on Pesaḥ is any one of the five species of cereal grains that came into contact with water and fermented. The five species are wheat (ḥitta), barley (se’ora), oats (the common identification of the “shibolet shu’al” mentioned by the Sages), rye (shifon), and spelt (kusmin). These species are used to make bread, the staple food of mankind. The Sages ordained a special blessing to be recited before eating bread – “Who brings forth bread from the earth” (“ha-motzi leḥem min ha-aretz”). After eating bread, the Torah commanded us to recite Birkat Ha-mazon. So that bread will be tasty and easy to digest, its dough is fermented and made to rise.

There are two types of leaven products: ḥametz and se’or. Both are produced by mixing flour and water. Common ḥametz is the leavening of the dough to bake bread and cakes. The leavening is done by leaving the dough at rest without handling it. If one wants to accelerate the leavening, one mixes se’or (starter dough) into the dough. Se’or (akin to sourdough) is the second type of leaven product. It is produced by leaving ḥametz for a long time, so that it continues to effervesce and ferment, until it tastes so sour that it is not fit for human consumption. The purpose of se’or is to hasten and improve the quality of leavening of various types of dough, for the preparation of breads and cakes. In other words, ḥametz is intended for eating while se’or is a leavening agent in preparing ḥametz foods. The Torah prohibited both, and the law is the same regarding both. One who leaves a kezayit of either of them in his possession during Pesaḥ violates bal yera’eh and bal yimatzei (Beitza 7b).

But if flour of the five cereal grains is mixed with water, kneaded rapidly, and put it into an oven immediately, then the dough will not have enough time to rise. This is the matza that we are commanded to eat on the first night of Pesaḥ, as a commemoration of the Exodus from Egypt, as is written, “And the people picked up their dough before it leavened” (Shemot 12:34). Thus, specifically those species of grain that may become ḥametz are the species from which one makes matza for the mitzva (Pesaḥim 35a).

Although rice and millet are similar to the five species of cereal grain, and although they rise, they do not undergo a complete fermentation process as the five cereal species do. Therefore, the prohibition against ḥametz does not apply to them, and if one made matza out of one of them, one does not fulfill any mitzva with it on Pesaḥ.

Note that kusmin (spelt) is not the same as kusemet (buckwheat). The former is one of the five species of cereal grain, whereas the latter is a type of legume and may be eaten on Pesaḥ by those who eat kitniyot; even among those who do not eat kitniyot, it is permitted for sick people (MB 453:4, 7; note well that some mix up the names and call spelt kusemet).

04. Defining the Leavening of Dough

As we have learned, the difference between bread and matza is that the dough used for making bread has undergone a leavening process resulting from the fermentation of ingredients within the flour that have come into contact with water. In order to augment the leavening process, bakers customarily mix se’or into the dough, causing the dough to ferment more thoroughly and quickly. However, even without the leavening agent, if dough is left without kneading, it would ferment and rise. Therefore, when preparing matzot, one must work quickly to ensure that the leavening process within the dough does not begin.

As long as the dough is in motion, being kneaded, it does not become ḥametz. Even if the kneading were to continue an entire day, the dough would not become ḥametz, since kneading arrests the leavening process. However, if the dough sits motionless for 18 minutes, the leavening process will begin and all the prohibitions concerning ḥametz will apply to it.

This applies to normal conditions, but where it is hotter, the leavening process is accelerated and the dough becomes ḥametz in even less than 18 minutes.

Cracks appearing in the dough are a physical indication that the dough has become ḥametz. Even if 18 minutes without kneading had not yet passed, since cracks formed in the dough, it has certainly become ḥametz; apparently it was warm so it took less time to become ḥametz, or the kneading was inadequate and certain parts of the dough were neglected, causing those areas to become ḥametz. Even if there are very few cracks, and they appeared only in part of the dough, the entire dough is ḥametz. If no cracks appeared but the dough blanched, it is ḥametz nuksheh (hardened ḥametz; see next section), which is rabbinically forbidden (SA 459:2).[3]


[3]. The rising of the dough indicates that it has become ḥametz (Me’iri), and other indications, like cracks in the dough, a blanched appearance, and the amount of time that has elapsed, are only relevant in a case where the dough did not rise. However, there are situations in which the dough rises without becoming ḥametz; rather, it has undergone what the Sages call “sirḥon” (spoilage). This applies to the case of rice and of flour mixed with fruit juice. However, when wheat flour mixes with water and begins to rise, it indicates that the mixture has become ḥametz. If the dough sat and was not kneaded for the time that it takes to walk one mil, it has become ḥametz even if there is no visible indication, as explained in the Mishna and Gemara in Pesaḥim 46a. SA 459:2 explains that this amount of time is 18 minutes, although Rambam and R. Ovadia of Bertinoro maintain that it is 24 minutes. BHL ad loc. states that it is possible to rely on the lenient position to prevent a significant loss, but under normal circumstances, because of the strict nature of the prohibition of ḥametz, the poskim adopt the eighteen-minute period without even mentioning the more lenient opinion.

According to Rashi and Me’iri, however, one must check the amount of time that the dough has been sitting only when it is unclear whether or not the leavening process has begun: if more than the time it takes to walk one mil has elapsed, the dough is ḥametz. If one is certain that the dough is not ḥametz, even if it has been sitting for longer than the time that it takes to walk one mil, it is not considered ḥametz. Nonetheless, according to most Rishonim in any situation where the dough has sat for longer than it takes to walk one mil, the dough is ḥametz. This is the ruling in MT, Laws of Ḥametz and Matza 5:13 and SA 459:2. Pri Megadim’s introduction to §467 contends that such dough is complete ḥametz; eating it on Pesaḥ incurs the punishment of karet. Rashbatz writes that one must suspect that such dough has become ḥametz. In a warm place, dough becomes ḥametz in less than the time it takes to walk a mil, as written in Aguda in the name of the Ge’onim. This is the halakhic consensus, as it is also the ruling of Yerei’im, Hagahot Maimoniyot, and Mordechai. Additionally, Rosh writes that even if the dough became warm in one’s hands, the dough will become ḥametz more quickly. This is cited in SA and Rema 459:2 (see also Berur Halakha on Pesaḥim 46a). Although there is dispute as to whether or not the “sitting times” of the dough are combined, Terumat Ha-deshen rules that a full kneading of the dough cancels the previous sitting time, though merely poking the dough would not be effective. This is cited in MB 459:16.

Pesaḥim222222 48b states: “As long as the dough is being worked it cannot become ḥametz.” The vast majority of Rishonim, including MT, Laws of Ḥametz and Matza 5:3 and Tur and SA 459:2, explain that as long as one keeps kneading the dough it will not become ḥametz, even if he does so for the entire day. Yet it appears that the Yerushalmi disagrees with the Bavli and says that if one kneaded the dough for the amount of time that it takes to walk four mil, the dough is considered ḥametz. Baḥ cites Ri’az that ideally we should act in accordance with the Yerushalmi. There is an even more stringent opinion – Ritva’s – according to which as long as one kneads the dough at the appropriate pace so that he will complete the kneading in less time than it would take to walk one mil, the dough does not become ḥametz. However, if the kneading goes on for longer than this time, the dough is considered ḥametz. Even though the vast majority of poskim disagree with Ritva, they rule that lekhatḥila we are strict about finishing the kneading process within 18 minutes, as explained in AHS 459:7.

05. Ḥametz Nuksheh (Hardened Ḥametz)

The ḥametz that the Torah forbade is ḥametz gamur (absolute ḥametz), meaning that the leavening process has been completed, and the food has become edible. But if fermentation had begun but not concluded, and if the food is edible under pressing circumstances, then it is “ḥametz nuksheh.” According to most poskim, ḥametz nuksheh is not forbidden by the Torah, but the Sages prohibited it so that people would not err and come to eat or keep real ḥametz.

An example of ḥametz nuksheh is the glue that scribes used to prepare from flour and water for gluing paper. Since its leavening process was never completed, and it is barely edible, it is ḥametz nuksheh, and the Sages forbade eating it or keeping it on Pesaḥ (MB 442:2). If its form was changed, as when the glue is used to stick papers together, then one is allowed to keep it. Others are more stringent and maintain that if the glue protrudes from between the pages, then it is considered as if it has maintained its same form, and it is forbidden to keep it on Pesaḥ (SA and Rema 242:3).

Similarly, dough that began to ferment to the point that its surface blanched, but the surface was not cracked as with true leavening, is ḥametz nuksheh, and it is forbidden by rabbinic law to eat or keep it on Pesaḥ (SA 459:2).[4]


[4]. The opinion of SA 447:12 is that ḥametz nuksheh is only rabbinically forbidden, and therefore, ḥametz nuksheh that existed over Pesaḥ is not forbidden after Pesaḥ. This is also the opinion of SAH 442:20-21 and MB 442:2, based on the opinion of most Rishonim. However, several Rishonim maintain that ḥametz nuksheh is forbidden by Torah law. There are two related issues: the prohibition of eating ḥametz nuksheh and the prohibition of keeping ḥametz nuksheh (see Berur Halakha on Pesaḥim 48b regarding the issue of eating, and 42a regarding the issue of keeping it over Pesaḥ). According to Rabbeinu Tam and many other poskim, flour that is mixed with fruit juice and a little bit of water is also considered ḥametz nuksheh. See below (8:1) regarding matza ashira.

06. Ḥametz So Spoiled That a Dog Would Not Eat It

Ḥametz that was originally fit for eating, but that became moldy or spoiled to the point that it is not fit for human consumption, is still considered ḥametz gamur, since it can still be used as a leavening agent. In this respect, ḥametz differs from all other forbidden foods, which are no longer forbidden once they become unfit for human consumption. Ḥametz, in contrast, remains forbidden even when it becomes unfit for human consumption, since it can still serve as a starter for another dough. Only if the ḥametz became so spoiled that it is unfit for consumption by a dog, it is not considered food at all, it no longer has the status of ḥametz, and it is permissible to keep it during Pesaḥ and to derive benefit from it (SA 442:2; MB 10). By rabbinic decree, however, it is still forbidden to eat it on its own, for by eating it one shows that he considers it food (MB 442:43). The same principle applies to all food prohibitions: Even if it is no longer fit for human consumption, the Sages forbid eating it.

The yardstick of being fit for a dog’s consumption is relevant only for measuring the spoilage of ḥametz or se’or. But if se’or was not spoiled, but only became so sour that it is not fit even for a dog, since it is good se’or (that functions as a leavening agent and is usable like regular yeast), all the laws of ḥametz apply to it, and one is required by Torah law to destroy it (BHL 442:9).

This law – that one does not have to burn ḥametz that was spoiled to the point of not being fit for a dog’s consumption – applies only if it became spoiled before the time that ḥametz becomes prohibited. But if it was fit to be eaten by a dog when the prohibition of ḥametz began, then even if it became spoiled later, to the point of being unfit for a dog’s consumption, one must eliminate it. Since the mitzva of eliminating the ḥametz has taken effect, one has not discharged his obligation until he has destroyed the ḥametz completely (MB 442:9; see below, ch. 5, n. 5).[5]

It is important to note that all of these laws are conditional on the ḥametz having initially been fit for human consumption or for preparing human food, like starter dough. But if it was never fit for human consumption, even if it was fit to be eaten by a dog, the prohibition of ḥametz never applied to it. However, the ḥametz in food prepared for dogs and cats was initially fit for human consumption, and it therefore must be eliminated. Something that was not initially meant for eating but was, in fact, fit for human consumption under pressing circumstances is ḥametz nuksheh, as described above.


[5]. MB 442:44 cites Ḥok Yaakov, which quotes Terumat Ha-deshen that if a gentile prepared ḥametz on Pesaḥ and then made it inedible even for dogs, it is prohibited for a Jew to gain any benefit from it, since it had been proper ḥametz during a time when ḥametz was forbidden. See also Igrot Moshe OḤ 3:62, which is lenient in this matter. Yeḥaveh Da’at 2:60 summarizes the opinions regarding this issue. See AHS YD 103:1-5 regarding other forbidden foods that are no longer prohibited when they become unfit for human consumption.

07. Ways in Which There Is No Leavening

As noted, there are five types of grain that can become ḥametz after touching water. However, if they are roasted in fire, they can no longer become ḥametz, and in principle they may be mixed with water. Nevertheless, the Sages were concerned lest the roasting not be thorough, and thus the grain would become ḥametz when coming into contact with water. Therefore, one must treat them just as one treats regular cereal grains. If they became wet and 18 minutes passed, we suspect they may have become ḥametz, and it is forbidden to gain any benefit from them; one must destroy them (SA 463:3; MB ad loc 7).

The above concerns kernels of grain that were roasted in fire, but if it was flour that was roasted, there are Rishonim who are lenient, maintaining that one need not suspect that the flour was not roasted well. Thus, it is permissible to mix such flour with water or in a cooked food without concern for ḥametz (Rashi, Rambam). Many Rishonim hold that in the case of flour, as well, one must be concerned that it may have not been roasted thoroughly (Rabbeinu Yeruḥam, Hagahot Smak, Hagahot Maimoniyot, and others). The Aḥaronim rule that one must not mix roasted flour with water or in a cooked food, lest it become ḥametz. Nevertheless, if one did make such a mixture, even though it is forbidden to eat it, it is permissible to keep it until after Pesaḥ and to eat it then (MB 463:8; Kaf Ha-ḥayim ad loc. 13).

However, concerning matza that was properly baked, it is agreed that it cannot become leavened. Accordingly, it is permissible to soak matza and matza meal in water, and, indeed, this is what most people do. Ḥasidim, however, customarily do not eat soaked matza (see below, 8:2).

Scalding the grains or the flour in boiling water also destroys the capacity for becoming ḥametz. However, the Ge’onim prohibited reliance on scalding, for today no one knows how to do this scalding, and if the boiling does not destroy the potential for becoming ḥametz, an opposite process of rapid fermentation may be generated, as heat may hasten fermentation. Therefore, scalded grains or flour are treated just like ḥametz: it is forbidden to gain any benefit from them and one must burn them (SA 454:3; MB 13).

Flour on which water dripped, drop by drop, continuously, even all day long, does not become ḥametz, since the falling of the drops disturbs the flour and shakes it, and does not allow the leavening process to develop. Immediately upon cessation of the dripping, one should knead the dough and bake it. If there is doubt that some of the dripping may not have been continuous, then this is a doubt concerning a law of Torah, and one must relate to that flour as ḥametz and burn it (Pesaḥim 39b; SA 466:6).

Another way to prevent the dough from fermenting is by soaking it in cold water (Pesaḥim 46a; SA 457:2). Preferably, one should not do so, lest the water not be cold enough, allowing the dough to ferment (Rosh, MB 454:18).[6]

Flour that was kneaded with fruit juice does not become leavened at all, but if even a little water was added to the mixture, then it will become leavened (as explained below, 8:1).


[6]. Does freezing the dough halt the leavening process? According to Igrot Moshe OḤ 3:59, one may not assume it does, since perhaps the cold just slows down the leavening process but does not stop it completely. On the other hand, Ḥelkat Yaakov 3:166 and Devar Yehoshua 2:58 are lenient based on the fact that freezing the dough stops the leavening process completely. Nevertheless, one should not purposely prepare dough to freeze and bake on Pesaḥ, but if one prepared dough before Pesaḥ and did not have a chance to bake it before Pesaḥ, as long as the dough has not yet risen, he may freeze the dough and bake it after Pesaḥ.

And even though we generally are not lenient when it comes to scalding the dough, there are practical applications when dealing with a dangerously sick person, where it is better to minimize the number of prohibitions involved, as explained in MB 454:13.

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