Numbers 18:7-9 New Revised Standard Version, Anglicised Catholic Edition (NRSVACE)
7 But you and your sons with you shall diligently perform your priestly duties in all that concerns the altar and the area behind the curtain. I give your priesthood as a gift;[a] any outsider who approaches shall be put to death.
The Priests’ Portion
8 The Lord spoke to Aaron: I have given you charge of the offerings made to me, all the holy gifts of the Israelites; I have given them to you and your sons as a priestly portion due to you in perpetuity. 9 This shall be yours from the most holy things, reserved from the fire: every offering of theirs that they render to me as a most holy thing, whether grain-offering, sin-offering, or guilt-offering, shall belong to you and your sons.