2 Chronicles 23:4-6

4This is the thing which ye shall do: a third part of you that come in on the sabbath, of the priests and of the Levites, shall be keepers of the doors;

5and 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 Jehovah.

6But let none come into the house of Jehovah except the priests and those of the Levites that do the service; they shall go in, for they are holy; but all the people shall keep the watch of Jehovah.