Numbers 18:12, 17

“All the best of the olive oil and all the best of the wine and of the wheat, the first fruits of these things that they give to the LORD, I have given to you.

But you must not redeem the firstborn of a cow or a sheep or a goat; they are holy. You must splash their blood on the altar and burn their fat for an offering made by fire for a pleasing aroma to the LORD.