Numbers 1:48-50

48For Jehovah spake unto Moses, saying, 49Only the tribe of Levi thou shalt not number, neither shalt thou take the sum of them among the children of Israel; 50but appoint thou the Levites over the tabernacle of the testimony, and over all the furniture thereof, and over all that belongeth to it: they shall bear the tabernacle, and all the furniture thereof; and they shall minister unto it, and shall encamp round about the tabernacle.