And three of the thirty chief went down, and came to David in the harvest time unto the cave of Adullam: and the troop of the Philistines pitched in the valley of Rephaim. And three of the thirty - The word שלשים shalishim, which we translate thirty, probably signifies an office or particular description of men. Of these shalishim we have here thirty-seven, and it can scarcely be said with propriety that we have thirty-seven out of thirty; and besides, in the parallel place, 1 Chronicles 11:11-47, there are sixteen added. The captains over Pharaoh's chariots are termed שלשים shalishim, Exodus 14:7.
The Philistines pitched in the valley of Rephaim - This is the same war which is spoken of 2 Samuel 5:17, etc.