Numbers 18:4-6

New Revised Standard Version, Anglicised Catholic Edition

⁴ They are attached to you in order to perform the duties of the tent of meeting, for all the service of the tent; no outsider shall approach you. 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.