Exodus 12:22

19 Seven days shall there be no leaven found in your houses: for whosoever eateth that which is leavened, even that soul shall be cut off from the congregation of Israel, whether he be a stranger, or born in the land.

20 Ye shall eat nothing leavened; in all your habitations shall ye eat unleavened bread.

21 Then Moses called for all the elders of Israel, and said unto them, Draw out and take you a lamb according to your families, and kill the passover.

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

23 For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer to come in unto your houses to smite [you].

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

25 And it shall come to pass, when ye be come to the land which the LORD will give you, according as he hath promised, that ye shall keep this service.