Exodus 12:23-25

Revised Standard Version

²³ For the Lord will pass through to slay 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 slay you. ²⁴ You shall observe this rite as an ordinance for you and for your sons for ever. ²⁵ And when you come to the land which the Lord will give you, as he has promised, you shall keep this service.