15 War broke out again between the Philistines and Israel. David and his men went down to fight. David became exhausted. 16 Ishbi-Benob, a warrior descended from Rapha, with a spear weighing nearly eight pounds and outfitted in brand-new armor, announced that he'd kill David. 17 But Abishai son of Zeruiah came to the rescue, struck the Philistine, and killed him. Then David's men swore to him, "No more fighting on the front-lines for you! Don't snuff out the lamp of Israel!"
18 Later there was another skirmish with the Philistines at Gob. That time Sibbecai the Hushathite killed Saph, another of the warriors descended from Rapha.
Matthew Henry's Commentary on 2 Samuel 21:15-18
Commentary on 2 Samuel 21:15-22
(Read 2 Samuel 21:15-22)
These events seem to have taken place towards the end of David's reign. David fainted, but he did not flee, and God sent help in the time of need. In spiritual conflicts, even strong saints sometimes wax faint; then Satan attacks them furiously; but those who stand their ground and resist him, shall be relieved and made more than conquerors. Death is a Christian's last enemy, and a son of Anak; but through Him that triumphed for us, believers shall be more than conquerors at last, even over that enemy.