Numbers 18:3-6

3They are to perform their duties for you and for all matters related to the Tent. They must not approach the implements of the Sanctuary or the altar—otherwise, both you and they will die.

4They are to team with you and attend to the Tent of Meeting, for all the service of the Tent. But no unauthorized person may intrude upon you.

5So you are to attend to the Sanctuary and the care of the altar, so no further wrath will fall on Bnei-Yisrael.

6“See, I have personally taken your kinsmen, the Levites, from among Bnei-Yisrael as a gift for you and your sons with you, dedicated to Adonai to serve in the work of the Tent of Meeting.