2 Chronicles 23:3 (KJV)

And in the seventh year Jehoiada strengthened himself, and took the captains of hundreds, Azariah the son of Jeroham, and Ishmael the son of Jehohanan, and Azariah the son of Obed, and Maaseiah the son of Adaiah, and Elishaphat the son of Zichri, into covenant with him.

And they went about in Judah, and gathered the Levites out of all the cities of Judah, and the chief of the fathers of Israel, and they came to Jerusalem.

And all the congregation made a covenant with the king in the house of God. And he said unto them, Behold, the king’s son shall reign, as the Lord hath said of the sons of David.

This is the thing that ye shall do; A third part of you entering on the sabbath, of the priests and of the Levites, shall be porters of the doors;

And a third part shall be at the king’s house; and a third part at the gate of the foundation: and all the people shall be in the courts of the house of the Lord.