Numbers 18:15-16

Revised Standard Version Catholic Edition

¹⁵ Everything that opens the womb of all flesh, whether man or beast, which they offer to the Lord, shall be yours; nevertheless the first-born of man you shall redeem, and the firstling of unclean beasts you shall redeem. ¹⁶ And their redemption price (at a month old you shall redeem them) you shall fix at five shekels in silver, according to the shekel of the sanctuary, which is twenty gerahs.