So I apply the psalm here, asking: Are you faithful in this sense? Is your heart steadfast? Alexander Maclaren has a sermon on this verse titled "The Fixed Heart" in which he provides some wise words and asks some searching questions:
I want to deal now with part two of this psalm, holding consideration of the chorus or refrain for last. Generally speaking, part two has the same themes as part one. But I want you to see how they are introduced and what happens to them the second time around. Seeing this will help you to understand something about Hebrew poetry.
The wings of God. The problem with the first image has led other commentators to explain David's reference as to the wings of God himself. To the objection that God does not have wings or that the image is unworthy of the Almighty we answer that God speaks along these lines himself in several places. Indeed, the earliest biblical use of the word "wings" is an example. In Exodus 19:4, God declares, "You yourselves have seen what I did to Egypt, and how I carried you on eagles’ wings and brought you to myself." This initial use of the image later lends itself to several variations. Thus, in the Song of Moses God is compared to an eagle that stirs up its nest and hovers over its young, that spreads its wings to catch them and carries them on its pinions (Deut. 32:11).
The first of the psalm's two parts begins with David asking for mercy, even as he takes refuge in God. Since the title of the psalm speaks of the cave in which David was hiding, it is natural to think that the cave suggested the idea of a "refuge.” But we should notice that David does not call the cave his refuge, though it was a refuge in a certain physical sense. Rather it is God whom he calls his refuge. Indeed, to use the image of the second half of verse 1, although David may have been hidden physically in the dark shadows of the vast cave of Adullam, he knows that it is actually under the shadow of the wings of God that he has found safety.
In the last several studies we have looked at psalms which are linked to that early desperate period of David's life when he was forced to flee into the wilderness from King Saul who wanted to kill him. Psalm 52 began this set of psalms. It refers to Doeg the Edomite who told Saul that David had gone to Nob and had been helped by Ahimelech the priest. Because of Doeg's self-serving betrayal Ahimelech and eighty-four of the priestly families were killed. Psalm 54 is another such psalm. It tells of David's betrayal by the Ziphites, who were his countrymen and who should have protected him. Worst of all, Psalm 56 describes David's desperate plight in the Philistine town of Gath which he went to alone, desperate and afraid.
