Exodus 12:21-28

21Then Moses called all the elders of Israel and said to them, "Go and select lambs for yourselves according to your clans, and kill the Passover lamb.

22Take a bunch of hyssop and dip it in the blood that is in the basin, and touch the lintel and the two doorposts with the blood that is in the basin. None of you shall go out of the door of his house until the morning.

23For the Lord will pass through to strike the Egyptians, and when he sees the blood on the lintel and on the two doorposts, the Lord will pass over the door and will not allow the destroyer to enter your houses to strike you.

24You shall observe this rite as a statute for you and for your sons forever.

25And when you come to the land that the Lord will give you, as he has promised, you shall keep this service.

26And when your children say to you, 'What do you mean by this service?'

27you shall say, 'It is the sacrifice of the Lord's Passover, for he passed over the houses of the people of Israel in Egypt, when he struck the Egyptians but spared our houses.'" And the people bowed their heads and worshiped.

28Then the people of Israel went and did so; as the Lord had commanded Moses and Aaron, so they did.