Numbers 18:15

15 Every firstborn that is offered to God, whether animal or person, is yours. Except you don't get the firstborn itself, but its redemption price; firstborn humans and ritually clean animals are bought back and you get the redemption price.

Numbers 18:15 In-Context

13 all the firstfruits they offer to God are yours. Anyone in your household who is ritually clean may eat it.
14 "You get every Totally-Devoted gift.
15 Every firstborn that is offered to God, whether animal or person, is yours. Except you don't get the firstborn itself, but its redemption price; firstborn humans and ritually clean animals are bought back and you get the redemption price.
16 When the firstborn is a month old it must be redeemed at the redemption price of five shekels of silver, using the standard of the Sanctuary shekel, which weighs twenty gerahs.
17 "On the other hand, you don't redeem a firstborn ox, sheep, or goat - they are holy. Instead splash their blood on the Altar and burn their fat as a Fire-Gift, a pleasing fragrance to God.
Published by permission. Originally published by NavPress in English as THE MESSAGE: The Bible in Contemporary Language copyright 2002 by Eugene Peterson. All rights reserved.