David
Psalm 3:3ESV·traditional attribution

But you, O LORD, are a shield about me, my glory, and the lifter of my head.

John Calvin Reformed @genevareformer

PSALM 3. David, although driven from his kingdom, and pressed down with utter despair of relief from every earthly quarter, ceases not to call upon God, and supports himself from his promise against the greatest terrors, against the mockery and cruel assaults of his enemies; and, finally, against death itself, which then forced itself upon his consideration.

Commenting on Psalm 3:1-8

C.H. Spurgeon Reformed Baptist @princeofpreachers

Here David avows his confidence in God. "Thou, O Lord, art a shield for me." The word in the original signifies more than a shield; it means a buckler round about, a protection which shall surround a man entirely, a shield above, beneath, around, without and within. Oh! what a shield is God for his people!

Matthew Henry Presbyterian @wholebiblehenry

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