Numbers 1:51-53

51 "And when the tabernacle is to go forward, the Levites shall take it down; and when the tabernacle is to be set up, the Levites shall set it up. The outsider who comes near shall be put to death.

52 "The children of Israel shall pitch their tents, everyone by his own camp, everyone by his own standard, according to their armies;

53 "but the Levites shall camp around the tabernacle of the Testimony, that there may be no wrath on the congregation of the children of Israel; and the Levites shall keep charge of the tabernacle of the Testimony."