Numbers 18:17-19

17But the firstborn of a cow, or the firstborn of a sheep, or the firstborn of a goat, thou shalt not ransom: they are holy. Thou shalt sprinkle their blood on the altar, and their fat shalt thou burn as an offering by fire for a sweet odour to Jehovah.

18And their flesh shall be thine; as the wave-breast and as the right shoulder shall it be thine.

19All the heave-offerings of the holy things, which the children of Israel offer to Jehovah, have I given thee, and to thy sons and to thy daughters with thee, by an everlasting statute: it shall be an everlasting covenant of salt before Jehovah unto thee and thy seed with thee.