King James Version
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;English Standard Version
For their duty was to assist the sons of Aaron for the service of the house of the LORD, having the care of the courts and the chambers, the cleansing of all that is holy, and any work for the service of the house of God.New International Version
The duty of the Levites was to help Aaron's descendants in the service of the temple of the LORD: to be in charge of the courtyards, the side rooms, the purification of all sacred things and the performance of other duties at the house of God.