Exodus 12:21-28

21And Moses called all the elders of Israel, and said to them, Seize and take yourselves lambs for your families, and kill the passover.

22And take a bunch of hyssop, and dip [it] in the blood that is in the bason, and smear the lintel and the two door-posts with the blood that is in the bason; and none of you shall go out of the door of his house until the morning.

23And Jehovah will pass through to smite the Egyptians; and when he sees the blood on the lintel, and on the two door-posts, Jehovah will pass over the door, and will not suffer the destroyer to come into your houses to smite [you].

24And ye shall observe this as an ordinance for thee and for thy sons for ever.

25And it shall come to pass, when ye are come into the land that Jehovah will give you, as he has promised, that ye shall keep this service.

26And it shall come to pass, when your children shall say to you, What mean ye by this service?

27that ye shall say, It is a sacrifice of passover to Jehovah, who passed over the houses of the children of Israel in Egypt when he smote the Egyptians and delivered our houses. And the people bowed their heads and worshipped.

28And the children of Israel went away, and did as Jehovah had commanded Moses and Aaron; so did they.