But if the household is too small for a lamb, let him share one with a neighbor who dwells nearby, in proportion to the number of persons: you shall contribute for the lamb according to what each household will eat.

You shall keep watch over it until the fourteenth day of this month; and all the assembled congregation of the Israelites shall slaughter it at twilight.

They shall take some of the blood and put it on the two doorposts and the lintel of the houses in which they are to eat it.

They shall eat the flesh that same night; they shall eat it roasted over the fire, with unleavened bread and with bitter herbs.

The Shabbat before Passover is called "Shabbat HaGadol" because of the miracle that was performed. RAMA: It's a custom at Mincha to recite the Haggadah from the section of Avadim Hayinu to L’chapeir al kol avonoseinu. (Minhagim)

Rabbi Yitzḥak says: The Holy One, Blessed be He, said: Let Obadiah come, who dwells among two wicked ones, Ahab and Jezebel, but did not learn from their actions; and he will prophesy concerning Esau the wicked, the progenitor of Edom, who dwelled among two righteous ones, Isaac and Rebekkah, but did not learn from their actions. Efrayim Miksha’a, a student of Rabbi Meir, said in the name of Rabbi Meir: Obadiah was an Edomite convert. Consequently, he prophesied with regard to Edom. And this is as people say: From and within the forest comes the ax to it, as the handle for the ax that chops the tree is from the forest itself.

Moses then summoned all the elders of Israel and said to them, “Go, pick out lambs for your families, and slaughter the passover offering.

(Exodus 12:21) "And Moses called to all the elders of Israel": We are hereby taught that he made them a beth-din. "and he said to them": The word went forth from Moses to Israel. These are the words of R. Yoshiyah. R. Yonathan says: The word went forth from Moses to say to the elders, and the elders (to say) to all of Israel. R. Yoshiyah said to him: Why is this different from all of the "sayings" in the Torah, which were from Moses to say to Israel? Here, too, from Moses to say to Israel. Why, then, is it written (here) "And Moses called to all the elders of Israel and he said to them (to Israel)"? (to show that) he accorded (special) honor to the elders. And thus did the Holy One Blessed be He say to Moses: "Moses, accord honor to the elders," viz. (Exodus 3:16) "Go and gather the elders of Israel, etc." And it is written (Ibid. 4:29) "And Moses and Aaron went and they gathered together the elders of Israel." "Draw forth and take for yourselves": "Draw forth" — he who possesses his own; "and take" (i.e., acquire) — he who does not possess his own. R. Yossi Haglili says (The meaning is:) "Draw away from idol worship and cleave to mitzvoth." R. Yishmael says: Scripture here comes to apprise us that one may number himself for (the eating of) the Paschal lamb, and he may "depart" from it, until it is slaughtered, so long as it is not left as is (i.e., without any owners.) R. Yitzchak says: Scripture (here) comes to teach us that a small beast is acquired by (the act of) "drawing forth." "and slaughter the Pesach: It is a mitzvah to slaughter it as a Pesach offering. If he does not offer it as such, he transgresses the mitzvah. I might think that in the above instance) it is, nevertheless kasher. It is, therefore, written (Ibid. 27) "It is a Paschal sacrifice to the L rd." Scripture repeats it to render it unfit (in the above instance.) From here it was ruled: All sacrifices which were slaughtered not "as such" are kasher, but they are not accounted to the owners as the fulfillment of an obligation — except for the Pesach and the sin-offering, (which are not kasher.)

The Sabbos before Pesach is called "Shabbat HaGadol" (The Great Shabbos). And the reason is because a miracle occurred during the Exodus from Egypt. On the 10th [they took a sheep] as it says: "On the tenth of this month you shall take for yourselves a sheep into your homes."
And the year that the Exodus took place was on a Thursday as we see in Seder Olam, and therefore the "10th of the month" was Shabbos, and [on that Shabbos] every Jew took a sheep as a Paschal offering and tied it to their bedposts. And the Egyptians asked them "Why is this so [why do you have a sheep (the Egyptian god) tied to your bed]?" And they responded: "To slaughter for a Pesach offering for HaShem." And they got upset that they were going to slaughter their gods, but they could not say anything due to the miracle. And thus it is called Shabbat HaGadol.