Numbers 18:15

15 “The firstborn of every mother, whether human or animal, that is offered to the LORD will be yours. But you must always redeem your firstborn sons and the firstborn of ceremonially unclean animals.

Numbers 18:15 In-Context

13 All the first crops of their land that the people present to the LORD belong to you. Any member of your family who is ceremonially clean may eat this food.
14 “Everything in Israel that is specially set apart for the LORD also belongs to you.
15 “The firstborn of every mother, whether human or animal, that is offered to the LORD will be yours. But you must always redeem your firstborn sons and the firstborn of ceremonially unclean animals.
16 Redeem them when they are one month old. The redemption price is five pieces of silver (as measured by the weight of the sanctuary shekel, which equals twenty gerahs).
17 “However, you may not redeem the firstborn of cattle, sheep, or goats. They are holy and have been set apart for the LORD . Sprinkle their blood on the altar, and burn their fat as a special gift, a pleasing aroma to the LORD .
Holy Bible. New Living Translation copyright© 1996, 2004, 2007, 2013 by Tyndale House Foundation. Used by permission of Tyndale House Publishers Inc., Carol Stream, Illinois 60188. All rights reserved.