4 They are to join you and be responsible for the care of the tent of meeting—all the work at the tent—and no one else may come near where you are.

Read Numbers 18:4 Using Other Translations

And they shall be joined unto thee, and keep the charge of the tabernacle of the congregation, for all the service of the tabernacle: and a stranger shall not come nigh unto you.
They shall join you and keep guard over the tent of meeting for all the service of the tent, and no outsider shall come near you.
The Levites must join you in fulfilling their responsibilities for the care and maintenance of the Tabernacle, but no unauthorized person may assist you.