Exodus 13:13

13:13 Every 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.

Exodus 13:15

13:15 When 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.’