Numbers 18:5-7

New Revised Standard Version, Anglicised Catholic Edition

⁵ You yourselves shall perform the duties of the sanctuary and the duties of the altar, so that wrath may never again come upon the Israelites. ⁶ It is I who now take your brother Levites from among the Israelites; they are now yours as a gift, dedicated to the Lord, to perform the service of the tent of meeting. 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.