Numbers 4:1-4

Then the LORD spoke to Moses and to Aaron, saying, “Take a census of the descendants of Kohath from among the sons of Levi, by their families, by their fathers’ households, from thirty years and upward, even to fifty years old, all who enter the service to do the work in the tent of meeting. This is the work of the descendants of Kohath in the tent of meeting, concerning the most holy things.