If it is an unclean animal, then he is to buy it back according to your valuation, and add a fifth of the value to it. But if it is not redeemed, then it is to be sold according to your valuation.
But the firstborn of the ox, sheep or goat you are not to redeem. They are holy. You are to sprinkle their blood on the altar, and their fat you are to burn as a fire offering, a pleasing aroma to Adonai.
because all the firstborn are Mine. In the day when I was striking down all the firstborn in the land of Egypt, I consecrated to Myself every firstborn in Israel—whether man or animal—as Mine. I am Adonai.”
“All the firstborn males that are born in your herd and your flock you are to consecrate to Adonai your God. You are to do no work with the firstborn of your herd or shear the firstborn of your flock.