Numbers 4:16, 28, 33

“Eleazar son of Aaron the priest will be responsible for the oil of the lampstand, the fragrant incense, the daily grain offering, and the anointing oil. In fact, Eleazar will be responsible for the entire Tabernacle and everything in it, including the sanctuary and its furnishings.”

So these are the duties assigned to the Gershonite clans at the Tabernacle. They will be directly responsible to Ithamar son of Aaron the priest.

So these are the duties of the Merarite clans at the Tabernacle. They are directly responsible to Ithamar son of Aaron the priest.”