2 Chronicles (Author Compiled by Isaiah and Ezra from records of Nathan, Gad, Iddo, Ahijah, Jehu and others.)
Chapter 23
6But 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.
Original from The Bible Foundation - bf.org. They claim public domain status for their original text.