Exodus 12:12-14, 23

“That night I will go through the land of Egypt and kill all the firstborn animals and people in the land of Egypt. I will also punish all the gods of Egypt. I am the LORD. But the blood will be a sign on the houses where you are. When I see the blood, I will pass over you. Nothing terrible will hurt you when I punish the land of Egypt. “You are always to remember this day and celebrate it with a feast to the LORD. Your descendants are to honor the LORD with this feast from now on.

When the LORD goes through Egypt to kill the Egyptians, he will see the blood on the sides and tops of the doorframes, and he will pass over that house. He will not let the one who brings death come into your houses and kill you.