Exodus 13:11-13

11“And it shall be, when the Lord brings you into the land of the Canaanites, as He swore to you and your fathers, and gives it to you,

12that you shall set apart to the Lord all that open the womb, that is, every firstborn that comes from an animal which you have; the males shall be the Lord’s.

13But every firstborn of a donkey you shall redeem with a lamb; and if you will not redeem it, then you shall break its neck. And all the firstborn of man among your sons you shall redeem.