Numbers 1:51-53

51 When the Dwelling is to move on, the Levites shall take it down; when the Dwelling is to be pitched, it is the Levites who shall set it up. Any layman who comes near it shall be put to death.

52 While the other Israelites shall camp by companies, each in his own division of the camp,

53 the Levites shall camp around the Dwelling of the commandments. Otherwise God's wrath will strike the Israelite community. The Levites, then, shall have charge of the Dwelling of the commandments."