Numbers 18:15 in the King James Version
Every thing that openeth the matrix in all flesh, which they bring unto the LORD, whether it be of men or beasts, shall be thine: nevertheless the firstborn of man shalt thou surely redeem, and the firstling of unclean beasts shalt thou redeem.
Context
14 “Everything devoted in Israel shall be yours.
15 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.
16 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.