Psalm 91 belongs to a transitional age, the age when Jerusalem, after David conquered it, became the religious capital of Yahwism and at the same time the capital of the newly created Jewish state. Before this, Jerusalem, then called Salem or, by the name of the tribe on whose territory it stood, Jebus, had been a sanctuary city, a sanctuary revered by all the surrounding tribes, where people worshiped a deity named El-Elyon, the local god of the sky, like Olympian Zeus in Greece. In the Synodal translation the name of this deity is usually rendered "God Most High," although the corresponding title would more accurately be translated "high" or "exalted."
In this case the issue is evidently a god of the sky, but not the God of Abraham, who revealed Himself to Abraham with the name El-Shaddai, usually translated "God Almighty," although it would be more accurate to translate it "God of power," if one translates it at all, since proper names are usually not translated, even though they have their own etymology. In Psalm 91, meanwhile, both epithets, Elyon, applied to the former master of the sanctuary, and Shaddai, applied to the God of Abraham, are applied to Yahweh.
The mention of feathers and wings in the text probably indicates that in pre-Yahwistic times El-Elyon was worshiped in the image of a bird, as often happened in antiquity in the Near East with gods of the sky, whose sacred bird was usually considered an eagle or a hawk. The application of both titles to the new master of the sanctuary, to Yahweh, says that He now takes the place of the former deity as the true God who replaces the pagan lord of the heavens. Yet behind the titles mentioned there stands, besides history as such, genuine spiritual experience.
Shelter, wings, shadow - all these are epithets used to describe the experience of what we usually call God's protection, provided of course that we do not understand this expression in a purely figurative or allegorical way. The sensation of the Presence really does sometimes resemble both a covering over the head and a light breath, as if from invisible wings. Such experience testifies to the nearness of God; then a person really can feel that God is carrying him, as it were, in His arms, so that he has absolutely nothing to fear. This experience may be considered quite universal, but like any experience, it is usually conveyed and described in the language of its age, a language sometimes unfamiliar to us, but entirely adequate from the point of view of those who used it.
