Matthew Poole and continuators on 2 Samuel 21:15

15 ¶ Moreover, the Philistines had yet war again with Israel , and David went down, and his servants with him, and fought against the Philistines, and David waxed faint.

These Wars though here related, were transacted long before this time: of which see the notes on v. 1. For it is no way probable, either, that the Philistines being so fully and perfectly subdued by David, chap. 8. 1. should in his days be in a capacity of waging War with the Israelites: or, that David in his old age would undertake to fight with a Giant, or that his people would permit him to do so.