Numbers 1:51

⁴⁹See, thou shalt not muster the tribe of Levi, and thou shalt not take their numbers, in the midst of the children of Israel.

⁵⁰And do thou set the Levites over the tabernacle of witness, and over all its furniture, and over all things that are in it; and they shall do service in it, and they shall encamp round about the tabernacle.

— Numbers 1:51 —

⁵²And the children of Israel shall encamp, every man in his own order, and every man according to his company, with their host.

⁵³But let the Levites encamp round about the tabernacle of witness fronting it, and so there shall be no sin among the children of Israel; and the Levites themselves shall keep the guard of the tabernacle of witness.