2 Chronicles 23:6
No one must enter the Lord's temple except the priests and Levites who are on duty. They may enter because they are ceremonially pure. All the others should carry out their assigned service to the Lord.
1 Chronicles 23:28-32
Their job was to help Aaron's descendants in the service of the Lord's temple. They were to take care of the courtyards, the rooms, ceremonial purification of all holy items, and other jobs related to the service of God's temple.
2 Kings 11:6-7
Another third of you will be stationed at the Foundation Gate. Still another third of you will be stationed at the gate behind the royal guard. You will take turns guarding the palace.