Albert Barnes Commentary 2 Chronicles 23:4

"This is the thing that ye shall do: a third part of you, that come in on the sabbath, of the priests and of the Levites, shall be porters of the thresholds;" — 2 Chronicles 23:4 (ASV)

The writer of Chronicles relates the orders that were given to the Levites; the author of Kings, those received by the royal bodyguard (see the note on 2 Kings 11:5).