Numbers 4:16, 27

“The appointed duty of Eleazar the son of Aaron the priest is the oil for the light, the sweet incense, the daily grain offering, the anointing oil, the oversight of all the tabernacle, of all that is in it, with the sanctuary and its furnishings.”

“Aaron and his sons shall assign all the service of the sons of the Gershonites, all their tasks and all their service. And you shall appoint to them all their tasks as their duty.