2 – General Rules of the Prohibition against Ĥametz

1. Four Mitzvot Concerning the Prohibition against Ĥametz

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

The first prohibition is to refrain from eating ĥametz, as it is written, “And ĥametz shall not be eaten” (Shemot 13:3). Our Sages taught that the prohibition against eating ĥametz on Pesaĥ includes not deriving any kind of benefit from the ĥametz. The Torah also says, “You shall not eat anything leavened; in all of your settlements you shall eat matzot” (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 Pesaĥ. It must be noted that the Torah was particularly stringent concerning the prohibition against eating ĥametz. Almost all of the Torah’s food prohibitions are punishable by lashes, while eating ĥametz on Pesaĥ is punishable by karet (extirpation), as it is written, “whoever eats ĥametz 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 ĥametz 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 leavening agent that one uses to make dough ferment. This verse means not only that se’or is forbidden, but also that no ĥametz may be found in our possession on Pesaĥ. This prohibition is often called bal yimatzei.

The third prohibition is that no ĥametz may be seen in our possession, as it is written: “Matzot shall be eaten seven days; and no ĥametz 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 Pesaĥ at least one olive’s bulk (kezayit) of ĥametz. If the volume of the ĥametz 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 ĥametz.

The fourth mitzva – a positive commandment – is to get rid of ĥametz and se’or in advance of Pesaĥ, 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).

2. The Times When Ĥametz Is Prohibited by Torah Law and by Rabbinic Law

Although the prohibition against ĥametz applies primarily during the seven days of Ĥag Ha-matzot, from the fifteenth through the twenty-first of Nisan, nevertheless we were commanded to remove ĥametz from our homes at noon on the fourteenth of Nisan, Erev Pesaĥ.

The prohibition against eating ĥametz also begins at noon on the fourteenth, as is written, “And you shall sacrifice the Pesaĥ [offering] to G-d … you shall not eat ĥametz with it” (Devarim 16:2-3). This prohibits the eating of ĥametz from the time fit for bringing the Pesaĥ sacrifice, i.e., at noon on the fourteenth of Nisan. This prohibition against eating ĥametz 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 ĥametz for an additional hour. They also forbade eating ĥametz for two extra hours, since on a cloudy day 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 zmanit”). Thus, one may eat ĥametz for the first four seasonal hours of the fourteenth. During the fifth hour it is rabbinically forbidden to eat ĥametz, but it is permissible to derive benefit from it by, for example, feeding it to an animal or selling it to a gentile. When the sixth hour of the day begins, possession of ĥametz becomes prohibited rabbinically, and if one forgot to sell it to a gentile, it must be destroyed. When midday arrives, that is, after the sixth hour ends, ĥametz 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 remove the ĥametz (see below 3:6 concerning the mitzva of removing the ĥametz).

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

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


[1]The  mitzva of removing the ĥametz applies from noon on the fourteenth, as it is written, “However, on the first day you shall remove the se’or from your houses” (Shemot 12:15). The Sages demonstrated from other verses that “the first day” refers to Erev Pesaĥ. Since the ĥametz 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 ĥametz must be in the middle of the day preceding Pesaĥ, that is, at noon (Pesaĥim 4b).

The prohibition against eating ĥametz and obtaining any benefit from it applies from noon on the fourteenth, according to R. Yehuda, as explained in Pesaĥim 28a. Rambam, as well as R. Yitzĥak ibn Gi’at, Rosh, and most Rishonim, ruled in accordance with this view. R. Shimon’s view is that the prohibition against eating ĥametz begins with the holiday itself, and it is only the mitzva of removing the ĥametz that comes into effect at noon on the fourteenth. Some Rishonim rule in accordance with this view, although they disagreed about what the mitzva of getting rid of ĥametz entails according to R. Shimon. Let us mention two approaches. According to Ramban and Raavad, since one must get rid of the ĥametz, he is also not allowed 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 ĥametz from the beginning of the sixth hour of the day. According to Ha-ma’or, the mitzva of disposing of the ĥametz does not imply a prohibition against eating it, since by eating it, one is, in fact, disposing of it (see Encyclopedia Talmudit, vol. 16, s.v. “ĥametz”, p. 66; Hilkhot Ĥag Be-ĥag, p. 8, n. 3). Again, the view of most poskim is that the halakha follows R. Yehuda’s view that the prohibition against eating ĥametz and the prohibition against deriving any benefit from ĥametz are of Torah origin, and apply from noon. This is how the halakha is decided in SA (443:1). 

[2]. This is the opinion of most poskim, since for these prohibitions the term “seven days” is stated explicitly; see MB 443:1 in the name of MA and others. However, SHT 443:2 states that not everyone agrees to this, and according to Rashi the prohibition starts on midday of the fourteenth. This also seems to be the opinion of Rabbeinu Ĥananel and Itur, namely, that according to R. Yehuda these prohibitions are like the prohibition of eating and begin at midday.

3. What Is Ĥametz and What Is Se’or?

The ĥametz that is prohibited by the Torah on Pesaĥ is any one of the five species of cereal grains that came into contact with water and fermented. The five species are wheat (ĥitta), barley (se’ora), oats (shibolet shu’al), 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 leĥem 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: ĥametz and se’or. Both are produced by mixing flour and water. Ĥametz is the regular leavening of dough to bake bread and cakes. The fermentation is accomplished by leaving the dough at rest without handling it. If one wants the leavening to be faster and of higher quality, one mixes se’or (sourdough) into the dough. Se’or is the second type of leavening. It is produced by leaving ĥametz for a long time, so that it continues to effervesce and ferment, until it tastes so sour that people cannot eat it. As noted, the purpose of se’or is to hasten and improve the quality of the leavening process of various types of dough, for the preparation of breads and cakes. More specifically, ĥametz is intended for eating while se’or is a leavening agent in preparing ĥametz 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 Pesaĥ 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 Pesaĥ, as a remembrance of the Exodus from Egypt, as is written, “And the people picked up their dough before it fermented” (Shemot 12:34). Thus, specifically those species of grain that may become ĥametz are the species from which one makes matza for the mitzva (Pesaĥim 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 ĥametz does not apply to them, and if one made matza out of one of them, one does not fulfill any mitzva with it on Pesaĥ.

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 Pesaĥ by those who eat kitniyot; even among those who do not eat kitniyot, it is permitted for sick people (MB 453:4, 7. Note that some mix up the names and call spelt kusemet).

4. The Definition of Leavening 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 were 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 ĥametz. Even if the kneading were to continue an entire day, the dough would not become ĥametz, since kneading inhibits the leavening process. However, if the dough sat motionless for eighteen minutes, the leavening process has begun and all the prohibitions concerning ĥametz apply to it. This applies to normal conditions, but where it is hotter, the leavening process is accelerated, and the dough becomes ĥametz in even less than eighteen minutes.

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


[3]. The rising of the dough indicates that it has become ĥametz (Me’iri), and other symptoms, namely, cracks in the dough, a blanched appearance, and the time that has elapsed, are only relevant in a case where the dough did not begin to rise. However, there are situations in which the dough rises but this does not indicate that it has become ĥametz; rather, it has undergone what the Sages call “sirĥon” (spoilage). This applies to the case of rice, or of flour mixed with fruit juice, according to most poskim. However, when wheat flour mixes with water and begins to rise, this is in fact a sign that the mixture has become ĥametz. If the dough sat and was not kneaded for the time that it takes to walk one mil, it has become ĥametz even if there is no visible indication, as explained in the Mishna and Gemara in Pesaĥim 46a. SA 459:2 explains that this amount of time is eighteen minutes, although Rambam and R. Ovadia of Bertinoro maintain that it is twenty-four minutes. BHL ad loc. rules that these lenient positions may be relied upon to prevent a significant loss of money, and that the authorities rule according to the Shulĥan Arukh without even mentioning the more lenient opinion because of the strict nature of the prohibition of ĥametz.

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 ĥametz, and vice versa. If one is certain that the dough is not ĥametz, even if it has been sitting for longer than the time that it takes to walk one mil, it is not considered ĥametz. 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 ĥametz. See, for example, MT, Laws of Ĥametz and Matza 5:13; SA 459:2. Pri Megadim’s introduction to §467 contends that such dough is complete ĥametz; eating it on Pesaĥ incurs the punishment of karet. Rashbatz writes that one must suspect that such dough has become ĥametz. In a warm place, dough becomes ĥametz 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, Mordechai, and Hagahot Maimoniyot. Additionally, Rosh writes that even if the dough became warm in one’s hands, the dough will become ĥametz more quickly. This is cited in SA and Rema 459:2 (see also Birur Halakha 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.

Pesaĥim222222 48b states: “as long as the dough is being worked it cannot become ĥametz.” The vast majority of Rishonim, including Rambam in Laws of Ĥametz and Matza 5:3 and Tur and SA 459:2, explain that as long as one keeps kneading the dough it will not become ĥametz, 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 ĥametz. Baĥ 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 ĥametz. However, if the kneading goes on for longer than this time, the dough is considered ĥametz (see Birur Halakha on Pesaĥim 48b; Encyclopedia Talmudit, s.v.ĥametz, §5, pp. 74-75). Even though the vast majority of poskim disagree with Ritva, they rule that it is still preferable to be stringent and complete the kneading process within eighteen minutes, as explained in AHS 459:7.

5. Ĥametz Nuksheh (Hardened Ĥametz)

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

An example of ĥametz 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 ĥametz nuksheh, and the Sages forbade eating it or keeping it on Pesaĥ (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 Pesaĥ (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 considered ĥametz nuksheh, and it is forbidden by rabbinic law to eat or keep it on Pesaĥ (SA 459:2).[4]


[4]. The opinion of SA 447:12 is that ĥametz nuksheh is only rabbinically forbidden, and therefore, ĥametz nuksheh that existed over Pesaĥ is not forbidden after Pesaĥ. This is also the opinion of SAH 442:20-21 and MB 442:2, based on the opinion of most Rishonim. However, several Rishonim are of the opinion that ĥametz nuksheh is forbidden by Torah law. There are two related issues: the prohibition of eating ĥametz nuksheh and the prohibition of keeping ĥametz nuksheh (see Birur Halakha on Pesaĥim 48b regarding the issue of eating, and 42a regarding the issue of keeping it over Pesaĥ). See also the Encyclopedia Talmudit entry “Ĥametz Nuksheh” p. 108 (definition) and pp. 110-115 (extent of the prohibition). According to Rabbeinu Tam and many other poskim, flour that is mixed with fruit juice and a little bit of water is also considered ĥametz nuksheh. See below (8:1) regarding matza ashira.

6. Ĥametz So Spoiled That a Dog Would Not Eat It

Ĥametz 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 ĥametz gamur, since it can still be used as a leavening agent. In other words, even though, in general, all forbidden foods become no longer forbidden once they are no longer fit for human consumption, ĥametz is different. Since it can still help in the preparation of food, it is like se’or, which serves as a leavening agent and is therefore considered ĥametz. However, if it became so spoiled that it is not fit for consumption by a dog, then it is not considered food at all. Therefore, the law of ĥametz does not apply to it and it is permissible to keep it during Pesaĥ and to gain benefit from it (SA 442:2; MB ad loc. 10). By rabbinic decree, however, it is still forbidden to eat it on its own, for one who eats it – even though he is doing something very unusual – demonstrates that he still considers this ĥametz to be food (MB 442, 43).

The yardstick of being fit for a dog’s consumption is relevant only for measuring the spoilage of ĥametz 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 ĥametz 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 ĥametz 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 ĥametz becomes prohibited. But if it was fit to be eaten by a dog when the prohibition of ĥametz began, then even if it became spoiled later, to the point of not being fit for a dog’s consumption, one must burn it. Once the mitzva of eliminating the ĥametz is in effect, one does not discharge his obligation until he has destroyed the ĥametz completely (MB 442:9; see below, ch. 5, n. 5).[5]

Note that all of these laws are conditional on the ĥametz having initially been fit for human consumption, or for preparing food for humans as se’or. If, however, it was not fit for human consumption at all from the beginning, then even if it was fit to be eaten by a dog, no prohibition applies to it. If from the beginning it was not intended for consumption, but it was in fact barely fit for human consumption, then it is ĥametz nuksheh, as described above.


[5]. MB 442:44 cites Ĥok Yaakov, which quotes Terumat Ha-deshen that if a gentile prepared ĥametz on Pesaĥ 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 ĥametz during a time when ĥametz was forbidden. See also Igrot Moshe OĤ  3:62, which is lenient in this matter. Yeĥaveh Da’at 2:60 summarizes the opinions regarding this issue. See also Bedikat Ĥametz U-vi’uro 2:27-32, which explains this topic at length, and in n. 87 explains that according to Rambam and Rosh, ĥametz that became inedible for humans and is still edible for dogs but would not cause any other dough to become ĥametz need not be burned; Raavad disagrees. See AHS YD 103:1-5 regarding other forbidden foods that are no longer prohibited when they become unfit for human consumption.

7. Ways in Which There Is No Leavening

As noted, there are five types of grain that can become ĥametz after touching water. However, if they are roasted in fire, they can no longer become ĥametz, 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 ĥametz when coming into contact with water. Therefore, one must treat them just as one treats regular cereal grains. If they became wet and eighteen minutes passed, we suspect they may have become ĥametz, and it is forbidden to gain any benefit from them, and 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 ĥametz (Rashi, Rambam). However, many Rishonim hold that in the case of flour, as well, one must be concerned that it may have not been roasted thoroughly (Rabbeinu Yeruĥam, Hagahot Sefer Mitzvot Katan, Hagahot Maimoniyot, and others). The Aĥaronim rule that one must not mix roasted flour with water or in a cooked food, lest it become ĥametz. Nevertheless, if one did make such a mixture, even though it is forbidden to eat it, it is permissible to keep it until after Pesaĥ and to eat it then (MB 463:8; Kaf Ha-ĥayim ad loc. 13).

However, concerning matza that was properly baked, it is agreed that it cannot become leavened again. Accordingly, it is permissible to soak matza and matza meal in water, and, indeed, this is what most people do. Ĥasidim, 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 ĥametz. However, the Ge’onim prohibited doing so, for today no one knows how to do this scalding, and if the boiling does not destroy the potential for becoming ĥametz, an opposite process of rapid fermentation may be generated, as heat may hasten fermentation. Therefore, scalded grains or flour are treated just like ĥametz: 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 ĥametz, 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 ĥametz and burn it (Pesaĥim 39b; SA 466:6).

Another way to prevent the dough from fermenting is by soaking it in cold water (Pesaĥim 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 (matza ashira will be explained below [8:1]).


[6]. Does freezing the dough halt the leavening process? Igrot Moshe OĤ  3:59 states that one may not assume that freezing halts the process, since perhaps the cold just slows down the leavening process but does not stop it completely. On the other hand, Ĥelkat 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 Pesaĥ, but if one prepared dough before Pesaĥ and did not have a chance to bake it before Pesaĥ, as long as the dough has not yet risen, he may freeze the dough and bake it after Pesaĥ.

All of the processes that slow the leavening process are summarized in the Encyclopedia Talmudit entry “Ĥametz” pp. 83-89. 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.