Exodus 12:17-30

You shall also observe the Feast of Unleavened Bread, because on this very day I brought your hosts [grouped according to tribal armies] out of the land of Egypt; therefore you shall observe this day throughout your generations as an ordinance forever. In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, [and continue] until the twenty-first day of the month at evening. Seven days no leaven shall be found in your houses; whoever eats what is leavened shall be cut off and excluded from [the atonement made for] the congregation of Israel, whether a stranger or native-born. [1 Cor 5:6-8] You shall eat nothing leavened; in all your dwellings you shall eat unleavened bread.’ ” Then Moses called for all the elders of Israel and said to them, “Go and take a lamb for yourselves according to [the size of] your families and slaughter the Passover lamb. You shall take a bunch of hyssop, dip it in the blood which is in the basin, and touch some of the blood to the lintel [above the doorway] and to the two doorposts; and none of you shall go outside the door of his house until morning. For the LORD will pass through to strike the Egyptians; and when He sees the blood on the lintel [above the entry way] and on the two doorposts, the LORD will pass over the door and will not allow the destroyer to come into your houses to slay you. You shall observe this event [concerning Passover] as an ordinance for you and for your children forever. When you enter the land which the LORD will give you, as He has promised, you shall keep and observe this service. When your children say to you, ‘What does this service mean to you?’ you shall say, ‘It is the sacrifice of the LORD’S Passover, for He passed over the houses of the Israelites in Egypt when He struck the Egyptians, but spared our houses.’ ” And the people bowed [their heads] low and worshiped [God]. Then the Israelites went and did [as they had been told]: just as the LORD had commanded Moses and Aaron, so they did. Now it happened at midnight that the LORD struck every firstborn in the land of Egypt, from the firstborn of Pharaoh who sat on his throne to the firstborn of the prisoner who was in the dungeon, and all the firstborn of the cattle. Pharaoh got up in the night, he and all his servants and all the Egyptians, and there was a great cry [of heartache and sorrow] in Egypt, for there was no house where there was not someone dead.