Numbers 18:15; Numbers 18:16

Numbers 18:15

15 The first offspring of every womb, both human and animal, that is offered to the LORD is yours. But you must redeem every firstborn son and every firstborn male of unclean animals.

Numbers 18:16

16 When they are a month old, you must redeem them at the redemption price set at five shekels of silver, according to the sanctuary shekel, which weighs twenty gerahs.