Exodus 12:12-14

Living Bible

¹² For I will pass through the land of Egypt tonight and kill all the oldest sons and firstborn male animals in all the land of Egypt, and execute judgment upon all the gods of Egypt—for I am Jehovah. ¹³ The blood you have placed on the doorposts will be proof that you obey me, and when I see the blood I will pass over you and I will not destroy your firstborn children when I smite the land of Egypt.

¹⁴ “You shall celebrate this event each year (this is a permanent law) to remind you of this fatal night.