Numbers 1:47-50

47But the Levites after the tribe of their fathers were not numbered among them. 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.