Mekhilta d’Rabbi Yishmael 12:6:1
(Exodus 12:6) “And it shall be to you for a keeping”: Why does the taking of the Pesach precede its slaughtering by four days? R. Matia b. Charash says: It is written (Ezekiel 16:8) “And I passed by you and I saw you, and behold, your time was the time for love”: There had arrived the (time for the fulfillment of the) oath that the Holy One Blessed be He had sworn to our father Abraham to redeem his children. But they had no mitzvoth to engage in, which would enable their redemption, viz. (Ibid. 7) “Your breasts were firm” (an allusion to Moses and Aaron), “and your hair had sprouted” (an allusion to the elders), but you were naked and bare” (of mitzvoth). And the Holy One Blessed be He gave them two mitzvoth — the blood of the Paschal lamb and the blood of circumcision to engage in for their redemption. Thus (Ibid. 6) “And I passed by you and I saw you steeped in your blood.” And it is written (Zechariah 9:11) “You, too — By the blood of your covenant I have sent forth your bound ones from the waterless pit.” Therefore, the Holy One Blessed be He commanded the taking of the Pesach four days before its slaughtering, for reward is given only for the act. R. Eliezer Hakappar Berebbi says: Did Israel not have four mitzvoth surpassing the worth of all the world? — not being suspect of illicit relations or of slander, not changing their names and not changing their language? Whence is it derived that they were not suspect of illicit relations? From (Leviticus 10:10) “And there went out the son of an Israelite woman, the son of an Egyptian man,” the verse apprising us of Israel’s eminence, this being the only instance of its kind, wherefore Scripture singles it out. And it is said of them in the tradition (Song of Songs 4:12) “A locked garden is my sister, my bride, a fountain locked.”: “a locked garden” — the women: “a fountain locked” — the men. R. Nathan says: “a locked garden” — the married women; “a fountain locked, a sealed up spring” — the betrothed women. Variantly: “a locked garden, a fountain locked” — an allusion to the two types of cohabitation. And whence is it derived that they were not suspect of slander and that they loved each other? From (Exodus 3:22) “And a woman shall ask of her neighbor, etc.” Twelve months had already passed, and we do not find an instance of one informing against another. And whence is it derived that they did not change their names? Just as they were called in their descent (to Egypt) — Reuven, Shimon, Levi, and Yehudah (viz. Ibid. 1:2) — so, they were called upon their ascent (viz. Numbers 1:18). And it is written (Genesis 48:16) “The angel who redeems me … and let there be called in them my name and the name of my fathers, etc.” And whence is it derived that they did not change their language? From (Ibid. 45:12) “… for the mouth that speaks to you” (speaks in the holy tongue), and (Exodus 5:3) “The G d of the Hebrews revealed Himself to us, etc.” and (Genesis 14:13) “And the survivor came and he told Avram the Hebrew, etc.” And why did the taking of the Pesach precede its slaughtering by four days? Because Israel was stepped in idolatry in Egypt, which countervails all of the mitzvoth, as it is written (Numbers 15:24) “And if from the eyes of the congregation it (idolatry) were done unwittingly, etc.” Scripture singled out this (idolatry, as tantamount to transgression of all of the mitzvoth [viz. Ibid. 22]). He said to them (viz. Exodus 12:21) “Withdraw” from idolatry (The sheep was the idolatry of Egypt), and cleave to mitzvoth. R. Yehudah b. Betheira says: It is written (Exodus 6:9) “And they would not hearken to Moses (as to G d’s delivering them), for shortness of spirit, etc.” Now is there anyone who is given glad tidings and does not rejoice? (viz. Jeremiah 20:14) “A son has been born to you — Rejoice him!” His Master is freeing him from bondage and he does not rejoice? What, then, is the intent of “And they would not hearken to Moses, etc.”? It was difficult for them to abandon their idolatry, viz. (Ezekiel 20:7) “And I said to them (in Egypt): Let every man cast away the detestations of his eyes and not defile himself with the idols of Egypt.” This is the intent of (Exodus 6:13) “And the L rd spoke to Moses and to Aaron, and He charged them to the children of Israel. He charged them to abandon idolatry. “And it shall be to you for a keeping”: What is the intent of this? It is written (Ibid. 12:21) “Draw forth and take for yourselves sheep, etc.” Israel said to Moses (Ibid. 8:22) “Will we slaughter the abomination of Egypt before their eyes and they (the Egyptians) not kill us?” He said to them: From the miracle that He will perform for you in your drawing them forth (i.e., their not protesting), you can rest assured (that no ill will befall you) in slaughtering them. “And it shall be to you for a keeping”: Keep it until the fourteenth (of Nissan) and slaughter it on the fourteenth. You say this, but perhaps (the meaning is) keep it and slaughter it until the fourteenth? It is, therefore, written (Numbers 9:5) “And they offered the Pesach in the first (month [Nissan]) on the fourteenth day of the month.” Scripture specified it (the fourteenth day) as mandatory. It is not the second assumption, then, that is to be accepted, but the first. “And it shall be to you for a keeping”: Scripture hereby apprises us that it was inspected (for possible blemishes) for (a period of) four days before being slaughtered. From here you learn (the same for) the tamid (the daily offering), viz. “keeping” is stated here, and “keeping” is stated in respect to the tamid. Just as the Pesach is observed four days before slaughtering, so, the tamid. From here they ruled: There are not to be fewer than six inspected lambs in the “chamber of lambs” (in the Temple), enough to suffice for a Sabbath accompanied by two festival days of Rosh Hashanah; and they are constantly replenished (as needed).