28 This is the service of the families of the sons of the Gershonites in the Tent of Meeting. Their duty shall be under the hand of Ithamar the son of Aaron the priest.
Numbers 4:28 Cross References - WEB
Numbers 4:33
33 This is the service of the families of the sons of Merari, according to all their service in the Tent of Meeting, under the hand of Ithamar the son of Aaron the priest.”