Exodus 13:10-15

10You must keep this ordinance at the appointed time year after year. 11“After the LORD brings you into the land of the Canaanites and gives it to you, as he promised on oath to you and your ancestors, 12you are to give over to the LORD the first offspring of every womb. All the firstborn males of your livestock belong to the LORD .

13Redeem with a lamb every firstborn donkey, but if you do not redeem it, break its neck. Redeem every firstborn among your sons. 14“In days to come, when your son asks you, ‘What does this mean?’ say to him, ‘With a mighty hand the LORD brought us out of Egypt, out of the land of slavery. 15When Pharaoh stubbornly refused to let us go, the LORD killed the firstborn of both people and animals in Egypt. This is why I sacrifice to the LORD the first male offspring of every womb and redeem each of my firstborn sons.’