Numbers 18:15-17

Amplified Bible

¹⁵ Every firstborn of the womb of all flesh, whether it is man or animal, which they bring to the Lord, shall be yours; nevertheless, the firstborn of man you shall most certainly redeem, and the firstborn of unclean animals you shall redeem. ¹⁶ And their redemption price, from a month old you shall redeem, according to your ^[a]valuation, for the [fixed] price of five shekels in silver, in accordance with the shekel of the sanctuary, which is twenty gerahs. ¹⁷ But the firstborn of a cow or of a sheep or of a goat you shall not redeem; they are holy [and belong to the Lord]. You shall sprinkle their blood on the altar and shall offer up their fat in smoke as an offering by fire, for a sweet and soothing aroma to the Lord.