Albert Barnes Commentary 2 Samuel 23:13

"And three of the thirty chief men went down, and came to David in the harvest time unto the cave of Adullam; and the troop of the Philistines was encamped in the valley of Rephaim." — 2 Samuel 23:13 (ASV)

The feat at Bethlehem by three of the thirty led to their being formed into a distinct triad. These three were probably Abishai (2 Samuel 23:18), Benaiah (2 Samuel 23:20), and a third man who is not named.

In the harvest time - This is likely an error for “to the rock” (compare the reference in the margin).

The troop of the Philistines - The word rendered “troop” occurs in this sense only here (and, according to some, in 2 Samuel 23:11) and perhaps in Psalm 68:11. In 1 Chronicles 11:15, as in 2 Samuel 23:16, the reading is “host” or “camp,” which may be the true reading here.

Pitched - This is the same Hebrew word translated as “encamped” in 1 Chronicles 11:15.

Valley of Rephaim - This means “Valley of the Giants” (see the note on 2 Samuel 21:16).