Numbers 18:14

“This is yours, too: the wave offering of their gift, even all the wave offerings of the children of Israel. I have given them to you, and to your sons and to your daughters with you, as a portion forever. Everyone who is clean in your house shall eat of it.

“I have given to you all the best of the oil, all the best of the vintage, and of the grain, the first fruits of them which they give to the LORD.

The first-ripe fruits of all that is in their land, which they bring to the LORD, shall be yours. Everyone who is clean in your house shall eat of it.

Everything that opens the womb, of all flesh which they offer to the LORD, both of man and animal, shall be yours. Nevertheless, you shall surely redeem the firstborn of man, and you shall redeem the firstborn of unclean animals.

You shall redeem those who are to be redeemed of them from a month old, according to your estimation, for five shekels of money, according to the shekel of the sanctuary, which weighs twenty gerahs.

“But you shall not redeem the firstborn of a cow, or the firstborn of a sheep, or the firstborn of a goat. They are holy. You shall sprinkle their blood on the altar, and shall burn their fat for an offering made by fire, for a pleasant aroma to the LORD.