Many there be which say of my soul, There is no help for him in God. Selah.
David, stripped of his kingdom and hunted by his own son, had every reason to despair, yet he clung to God's promise against mockery and death itself. He makes no mention of his sins here, his adultery and the blood of Uriah, which means this psalm captures only one part of his prayer; the full anguish of God's punishment for those crimes came first.
AI summary
Commenting on Psalm 3:1-8
David complains before his loving God of the worst weapon of his enemies' attacks, and the bitterest drop of his distresses. "Oh!" saith David, "many there be that say of my soul, There is no help for him in God." Some of his distrustful friends said this sorrowfully, but his enemies exultingly boasted of it, and longed to see their words proved by his total destruction.
The title of this psalm and many others is as a key hung ready at the door, to open it, and let us into the entertainments of it; when we know upon what occasion a psalm was penned we know the better how to expound it.
Commenting on Psalm 3:1-3