Numbers 18:9, 19

This shall be thine of the most holy things, reserved from the fire: every oblation of theirs, even every meal-offering of theirs, and every sin-offering of theirs, and every trespass-offering of theirs, which they shall render unto me, shall be most holy for thee and for thy sons.

All the heave-offerings of the holy things, which the children of Israel offer unto Jehovah, have I given thee, and thy sons and thy daughters with thee, as a portion for ever: it is a covenant of salt for ever before Jehovah unto thee and to thy seed with thee.