Numbers 18:17-19

17But 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.

18Their meat shall be yours, like the breast of a wave offering and like the right thigh.

19All the offerings of the holy things, which the Israelites offer to the Lord I have given to you and to your sons and your daughters with you as a continual allotment. It is an everlasting covenant of salt [that cannot be dissolved or violated] before the Lord to you and to your descendants with you.”