Exodus 12:1-7, 13

While the Israelites were still in the land of Egypt, the LORD gave the following instructions to Moses and Aaron: “From now on, this month will be the first month of the year for you. Announce to the whole community of Israel that on the tenth day of this month each family must choose a lamb or a young goat for a sacrifice, one animal for each household. If a family is too small to eat a whole animal, let them share with another family in the neighborhood. Divide the animal according to the size of each family and how much they can eat. The animal you select must be a one-year-old male, either a sheep or a goat, with no defects. “Take special care of this chosen animal until the evening of the fourteenth day of this first month. Then the whole assembly of the community of Israel must slaughter their lamb or young goat at twilight. They are to take some of the blood and smear it on the sides and top of the doorframes of the houses where they eat the animal.

But the blood on your doorposts will serve as a sign, marking the houses where you are staying. When I see the blood, I will pass over you. This plague of death will not touch you when I strike the land of Egypt.