Numbers 18:4-6

Amplified Bible, Classic Edition

⁴ And they shall be joined to you and attend to the duties of the Tent of Meeting—all the [menial] service of the Tent—and no stranger [no layman, anyone who is not a Levite] shall come near you [Aaron and your sons].

⁵ And you shall attend to the duties of the sanctuary and attend to the altar [of burnt offering and the altar of incense], that there be no wrath any more upon the Israelites [as in the incident of Korah, Dathan, and Abiram].^(A)

⁶ And I, behold, I have taken your brethren the Levites from among the Israelites; to you they are a gift, given to the Lord, to do the [menial] service of the Tent of Meeting.