Because their office was to wait on the sons of Aaron for the service of the house of the LORD, in the courts, and in the chambers, and in the purifying of all holy things, and the work of the service of the house of God;
Because they were responsible for assisting the descendants of Aaron with tasks related to the LORD's house, including the courtyards, rooms, and cleaning of all sacred items, as well as helping with the work in God's temple.