Exodus 13:12-15

12then you must give over to the Lord the first offspring of every womb. Every firstling of a beast that you have – the males will be the Lord’s.

13Every firstling of a donkey you must redeem with a lamb, and if you do not redeem it, then you must break its neck. Every firstborn of your sons you must redeem.

14In the future, when your son asks you ‘What is this?’ you are to tell him, ‘With a mighty hand the Lord brought us out from Egypt, from the land of slavery.

15When Pharaoh stubbornly refused to release us, the Lord killed all the firstborn in the land of Egypt, from the firstborn of people to the firstborn of animals. That is why I am sacrificing to the Lord the first male offspring of every womb, but all my firstborn sons I redeem.’