David Climbs the Mount of Olives Weepingby emmanuel_higgins

Psalms 3:2

Many there be which say of my soul, There is no help for him in God. Selah.

Many were saying of his soul that there was no help or deliverance for him in God. The taunt was spoken when David was in great danger, betrayed and deserted by his own son and by his subjects. Even while they said this, he kept his heart stayed upon God.

The surrounding verses expose the taunt as false, for the Lord is his shield, hears his prayer, sustains him, and gives him confidence even when many oppose him. In that setting the verse belongs to a comforting assurance for people in distress, including the sick and the dying.