Albert Barnes Commentary 1 Chronicles 26:12

"Of these were the courses of the doorkeepers, even of the chief men, having offices like their brethren, to minister in the house of Jehovah." — 1 Chronicles 26:12 (ASV)

This verse is obscure, but its probable meaning is as follows: "To these divisions of the gatekeepers—the chief men—were assigned the watches, along with their brothers, for service in the house of the Lord."

That is, the “chief men” (1 Chronicles 26:1–11), numbering only 93, performed guard duty for the house. They were assisted from time to time by an additional 4,000 of their brothers (1 Chronicles 23:5).