Charles Ellicott Commentary 1 Chronicles 11:42

"Adina the son of Shiza the Reubenite, a chief of the Reubenites, and thirty with him," — 1 Chronicles 11:42 (ASV)

A captain of the Reubenites (or, chief; Hebrew, head) and thirty with him (besides him)—literally, upon him.

The Septuagint and Syriac versions read, “and he was commanding thirty men,” which gives the apparent meaning of the verse.

If, as seems likely, “the thirty” were the officers of David’s guard of six hundred warriors (1 Samuel 23:13; 1 Samuel 30:10; 2 Samuel 15:18)—who were called “the mighty men,” or heroes (2 Samuel 10:7; 2 Samuel 20:7; 1 Kings 1:8)—then each captain would have led about twenty men.

Adina’s corps is mentioned, perhaps because it was larger than usual.