Numbers 3:32
And Eleazar the son of Aaron the priest shall be chief over the chief of the Levites, and have the oversight of them that keep the charge of the sanctuary. And Eleazar the son of Aaron the priest shall be chief over the chief of the Levites, and have the oversight of them that keep the charge of the sanctuary.
Eleazar, the son of Aaron the priest, was chief over the chiefs of the Levites and held the oversight of those who kept the charge of the sanctuary. Under him the Levites were arranged under a defined system of responsibilities, divided into groups with each given its own particular place and duty. Their charge included the care and the transporting of the tabernacle and its furnishings. That labor was distributed by family, with the Kohathites, the Merarites, and the Gershonites each assigned distinct duties. The sacred work of the sanctuary was reserved for those appointed to it, and each worker was to perform the task assigned to him and not take over the work of another.