Numbers 1:47-54

But the Levites were not numbered among them by their fathers’ tribe; for the LORD had spoken to Moses, saying: “Only the tribe of Levi you shall not number, nor take a census of them among the children of Israel; but you shall appoint the Levites over the tabernacle of the Testimony, over all its furnishings, and over all things that belong to it; they shall carry the tabernacle and all its furnishings; they shall attend to it and camp around the tabernacle. 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. The children of Israel shall pitch their tents, everyone by his own camp, everyone by his own standard, according to their armies; 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.” Thus the children of Israel did; according to all that the LORD commanded Moses, so they did.