Numbers 18:15-17

¹⁵Whatever openeth the womb of all flesh which they offer before the Lord, of man, or of beast, shall be for thee; but thou shalt surely redeem the firstborn of man, and the firstling of an unclean animal thou shalt redeem;

¹⁶And his redemption shall be at the age of one month; thou shalt redeem with the price of five shekes, in the shekel of the sanctuary it is ten meahs:

¹⁷But the firstling of an ox, or of a sheep, or of a goat, thou mayest not redeem, they are consecrated; thou shalt sprinkle their blood upon the altar, and burn their fat, an oblation to be accepted before the Lord.