Exodus 13:11-13 NIV
“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, you are to give over to the LORD the first offspring of every womb. All the firstborn males of your livestock belong to the LORD. Redeem with a lamb every firstborn donkey, but if you do not redeem it, break its neck. Redeem every firstborn among your sons.
NIV: New International Version