Numbers 1:48-50

For the LORD had spoken unto Moses, saying, Only thou shalt not number the tribe of Levi, neither take the sum of them among the children of Israel: But thou shalt appoint the Levites over the tabernacle of testimony, and over all the vessels thereof, and over all things that {belong} to it: they shall bear the tabernacle, and all the vessels thereof; and they shall minister unto it, and shall encamp round about the tabernacle.