Numbers 18:4-6 New King James Version (NKJV)

⁴ They shall be joined with you and attend to the needs of the tabernacle of meeting, for all the work of the tabernacle; but an outsider shall not come near you. ⁵ And you shall attend to the duties of the sanctuary and the duties of the altar, that there may be no more wrath on the children of Israel. ⁶ Behold, I Myself have taken your brethren the Levites from among the children of Israel; they are a gift to you, given by the Lord, to do the work of the tabernacle of meeting.