Exodus 13:11-13

11“When the Lord brings you into the land of the Canaanites, as he swore to you and your ancestors, and gives it to you,

12you are to present to the Lord every firstborn male of the womb. All firstborn offspring of the livestock you own that are males will be the Lord’s.

13You must redeem every firstborn of a donkey with a flock animal, but if you do not redeem it, break its neck. However, you must redeem every firstborn among your sons.