Charles Ellicott Commentary 1 Chronicles 11:23

"And he slew an Egyptian, a man of great stature, five cubits high; and in the Egyptian`s hand was a spear like a weaver`s beam; and he went down to him with a staff, and plucked the spear out of the Egyptian`s hand, and slew him with his own spear." — 1 Chronicles 11:23 (ASV)

And he slew an Egyptian... —Literally, and he it was who smote the Egyptian, a man of measure, five in the cubit. Samuel has only “who (was) a sight;” or “a man to look at” (Heb. margin). The chronicler says why.

Like a weaver’s beam. —Not in Samuel. Perhaps due to a recollection of the combat of David and Goliath. (Compare also 2 Samuel 21:19.) Yet the Septuagint of 2 Samuel 23:21 has “like the beam of a ship’s ladder” (ξύλον διαβάθρας); and this may be original.

Went down. —To the combat. (Compare Latin: descendere in aciem, etc.) The staff (shçbet) of Benaiah differs from David’s (maqqçl, 1 Samuel 17:40; 1 Samuel 17:43); and the similarity of the two accounts, so far as it extends, is a similarity not of fiction, but of fact.

With a staff. —Rather, the staff, which he happened to carry.