2 Chronicles 23:2-6

2And they went about through Judah and gathered the Levites from all the cities of Judah, and the heads of fathers' houses of Israel, and they came to Jerusalem.

3And all the assembly made a covenant with the king in the house of God. And Jehoiada said to them, "Behold, the king's son! Let him reign, as the Lord spoke concerning the sons of David.

4This is the thing that you shall do: of you priests and Levites who come off duty on the Sabbath, one third shall be gatekeepers,

5and one third shall be at the king's house and one third at the Gate of the Foundation. And all the people shall be in the courts of the house of the Lord.

6Let no one enter the house of the Lord except the priests and ministering Levites. They may enter, for they are holy, but all the people shall keep the charge of the Lord.