Exodus 12:23-28

For the LORD will pass through to smite 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 come in to your houses to smite you. And you shall observe this event as an ordinance for you and your children forever. When you enter the land which the LORD will give you, as He has promised, you shall observe this rite. And when your children say to you, ‘What does this rite mean to you?’ you shall say, ‘It is a Passover sacrifice to the LORD who passed over the houses of the sons of Israel in Egypt when He smote the Egyptians, but spared our homes.’ ” And the people bowed low and worshiped. Then the sons of Israel went and did so; just as the LORD had commanded Moses and Aaron, so they did.