2 Chronicles 23:6 (KJV)

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.

But let none come into the house of the Lord, save the priests, and they that minister of the Levites; they shall go in, for they are holy: but all the people shall keep the watch of the Lord.

And the Levites shall compass the king round about, every man with his weapons in his hand; and whosoever else cometh into the house, he shall be put to death: but be ye with the king when he cometh in, and when he goeth out.

So the Levites and all Judah did according to all things that Jehoiada the priest had commanded, and took every man his men that were to come in on the sabbath, with them that were to go out on the sabbath: for Jehoiada the priest dismissed not the courses.