Numbers 18:15-16

DouayRheims(i) 15 Whatsoever is firstborn of all flesh, which they offer to the Lord, whether it be of men, or of beasts, shall belong to thee: only for the firstborn of man thou shalt take a price, and every beast that is unclean thou shalt cause to be redeemed, 16 And the redemption of it shall be after one month, for five sicles of silver, by the weight of the sanctuary. A sicle hath twenty obols.