Numbers 18:17

But you must not redeem the firstborn of an ox, a sheep, or a goat; they are holy. You are to splatter their blood on the altar and burn their fat as a food offering, a pleasing aroma to the LORD.

But the firstling of a cow, or the firstling of a sheep, or the firstling of a goat, thou shalt not redeem; they are holy: thou shalt sprinkle their blood upon the altar, and shalt burn their fat for an offering made by fire, for a sweet savour unto the LORD.