Numbers 18:12-18

All the best of the fresh [olive] oil, and all the best of the new wine and of the grain, the first fruits of those which they give to the LORD, I give them to you. The first ripe fruits of all that is in the land, which they bring to the LORD, shall be yours; everyone in your household who is [ceremonially] clean may eat it. Every devoted thing in Israel [everything that has been promised to the Lord with an oath] shall be yours. 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. And their redemption price, from a month old you shall redeem, according to your valuation, for the [fixed] price of five shekels in silver, in accordance with the shekel of the sanctuary, which is twenty gerahs. 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. Their meat shall be yours, like the breast of a wave offering and like the right thigh.