Mekhilta d'Rabbi Yishmael 0.1.10

(Exodus 12:18) "On the first day, on the fourteenth day": Scripture made it mandatory (to eat matzoh on the first night).

"until the twenty-first day of the month in the evening." What is the intent of this? From (Ibid. 18) "Seven days shall you eat matzoth," I would know only of the days. Whence would I derive (the same for) the nights? It is, therefore, written "until the twenty-first day," to include the nights.

(Exodus 12:19) "Seven days se'or (leavening) shall not be found in your houses": This tells me only (that the transgression) against finding (it). Whence do I derive (the same for) seeing? From (Ibid. 13:7) "And se'or shall not be seen unto you in all of your boundaries." This tells me that only se'or is subject to the injunctions against being seen and being found. Whence do we derive (the same for) chametz? It is written (Ibid.) "Chametz shall not be seen unto you, and se'or shall not be seen unto you." Se'or is likened to chametz, and chametz to se'or. Just as the first (se'or) is subject to both, so, the second. Just as the second (chametz) is of the five species (of grain [see above]), so, the first.

(Ibid. 19) "In your houses": What is the intent of this? I might take (13:7) "in all of your boundaries," literally (i.e., even if the chametz is not yours); it is, therefore, written "in your houses." Just as your house is your domain, so "your boundaries" (applies only to chametz that is in your domain) — to exclude (from liability) the chametz of a Jew in the domain of a gentile. Even though he can remove it, it is not in his domain. And to exclude the chametz of a gentile in the domain of a Jew, and chametz under debris, where even though it is in his domain it cannot be removed. You say this, but perhaps the intent of the verse is that chametz is forbidden for "seven days" (viz. Ibid.), in the houses, and for all time, in the boundaries. It is, therefore, written (Devarim 16:4) "And chametz shall not be seen unto you in all of your border for seven days."

(Ibid. 19) "For whoever eats leavening, that soul shall be cut off": What is the intent of this? From (Ibid. 15) "Whoever eats chametz shall be cut off," I would know only of chametz. Whence would I derive (the same for) se'or? It is, therefore, written "For whoever eats leavening, that soul shall be cut off." — But even if it were not written, I would know it a fortiori, viz. If chametz, which does not cause other (foods) to become chametz, is liable to kareth, how much more so, se'or, which does cause other (foods) to become chametz! — No, this may be true of chametz, which is fit for eating — as opposed to se'or, which is not fit for eating, wherefore it should not be liable to kareth. It is, therefore, written "For whoever eats leavening, that soul shall be cut off." Let the verse for se'or suffice a fortiori for chametz, viz.: If se'or, which is not fit for eating, is liable to kareth, how much more so chametz, which is fit for eating! — No, this may be true of leaven, which causes other foods to become chametz — as opposed to chametz, which does not cause other foods to become chametz. The two verses, then, must be written. Otherwise, we would not know (the two laws).

(Exodus, Ibid. 19) "whether he be a proselyte or a citizen of the land": Because the act (i.e., the exodus) transpired only with Israel, proselytes had to be specially mentioned (for inclusion). The same applies with all acts which transpired only with Israel.

(Exodus 12:20) "All leavening you shall not eat": What is the intent of this? (Ibid. 15) "Whoever eats chametz, that soul shall be cut off" tells me of the punishment. Whence do I derive the exhortation? From "All leavening you shall not eat." This tells me only of them (i.e., chametz and leavening). Whence do I derive (the same for) their admixtures? From "All."

"In all of your habitations shall you eat matzoth": What is the intent of this? From (Devarim 14:23) "And you shall eat before the L–rd your G–d the tithe of your grain and wine and oil," I might think that if one brought up his second tithe to Jerusalem (and ate it there), he has fulfilled his obligation (of eating matzoh). It is, therefore, written "in all of your habitations" — to exclude this (tithe), which is not eaten in all places (but only in Jerusalem). And whence is it derived that he does not fulfill his obligation, neither with the show-bread, nor with the left-overs of meal-offerings, nor with the thanksgiving challoth, nor with the wafers of the Nazirite, nor with first-fruits? From "in all of your habitations shall you eat matzoth" — to exclude those, which are not eaten in all of your habitations.

It would follow that I exclude the aforementioned, but I include spongy dough, honey dough, pasty dough, pan-cakes, and pressed-cake. It is, therefore (to negate this) written (Devarim 16:3) "bread of affliction." These are the words of R. Yishmael.

The sages say: He fulfills his obligation with them and with second-tithe. And what is the intent of "bread of affliction"? That they are not to be kneaded with wine or oil or other liquids, but he may form it (the matzoh) with all of them.

R. Eliezer says: He fulfills his obligation with all of them and with second-tithe. And what is the intent of "bread of affliction"? Just as with the bread of a poor man, his wife kneads it and he heats it in the oven, so, here.

R. Yossi says: From "Seven days shall you eat matzoth" I understand, even (matzoth of) second-tithe. It is, therefore, written "bread of affliction," to exclude this (second-tithe), which is eaten only in joy.