"Now this shall be the priests' due from the people, from those who offer a sacrifice, either an ox or a sheep, of which they shall give to the priest the shoulder and the two cheeks and the stomach." (Deuteronomy 18:3)
"He is not to be concerned whether it is good or bad, nor shall he exchange it; or if he does exchange it, then both it and its substitute shall become holy. It shall not be redeemed.'" (Leviticus 27:33)