Numbers 1:49-52

49“Only the tribe of Levi you shall not number, nor shall you take their census among the sons of Israel [since they are unavailable to go to war].

50But appoint the Levites over the tabernacle (sanctuary) of the Testimony, and over all its furnishings and all things that belong to it. They shall carry the tabernacle [when traveling] and all its furnishings, and they shall take care of it and camp around it.

51When the tabernacle is to go forward, the Levites shall take it down; and when the tabernacle is to [be set up for] camp, the Levites shall set it up. But the layman (non-Levite) who approaches the tabernacle shall be put to death.

52The Israelites shall camp according to their armies, every man by his own camp and every man by his own [tribal] standard (banner).