John Wesley on 1 Samuel 27:1

I shall perish - But this was certainly a very great fault in David: for This proceeded from gross distrust of God's promise and providence; and that after such repeated demonstrations of God's peculiar care over him. He forsakes the place where god had settled him, chap.22:5, and given him both assurance and experience of his protection there. He voluntarily runs upon that rock, which he cursed his enemies for throwing him upon, chap.26:19, and upon many other snares and dangers, as the following history will shew; and withal, deprives the people of the Lord of those succours which he might have given them, in case of a battle. But God hereby designed to withdraw David from the Israelites, that they might fall by the hand of the Philistines, without any reproach or inconvenience to David.