Numbers 1:51

1:51 Whenever the tabernacle is to move, the Levites must take it down, and whenever the tabernacle is to be reassembled, the Levites must set it up. Any unauthorized person who approaches it must be killed.

Numbers 18:4

18:4 They must join with you, and they will be responsible for the care of the tent of meeting, for all the service of the tent, but no unauthorized person may approach you.