They were responsible for the care of the ark, the table, the lampstand, the altars, the articles of the sanctuary used in ministering, the curtain, and everything related to their use.
“Eleazar son of Aaron, the priest, is to have charge of the oil for the light, the fragrant incense, the regular grain offering and the anointing oil. He is to be in charge of the entire tabernacle and everything in it, including its holy furnishings and articles.”
All their service, whether carrying or doing other work, is to be done under the direction of Aaron and his sons. You shall assign to them as their responsibility all they are to carry.
They may assist their brothers in performing their duties at the tent of meeting, but they themselves must not do the work. This, then, is how you are to assign the responsibilities of the Levites.”