Charles Ellicott Commentary Psalms 103:5

"Who satisfieth thy desire with good things, [So that] thy youth is renewed like the eagle." — Psalms 103:5 (ASV)

Mouth. —On the Hebrew word rendered this way, see Psalms 32:9. The word adopted there (“trappings,” or “ornaments”) would recommend itself here, from the evident allusion in the next clause to the molting of the bird and its appearance in new plumage, if the expression “to satisfy ornament with good” were in any way intelligible. The Septuagint and Vulgate have “desire”; the Syriac “body”; but the Chaldee, “age,” which is supported (Gesenius) by the derivation, gives the best sense:—

Who satisfies your age with good, so that
Your youth renews itself like the eagle.

The eagle’s. —Hebrew, nesher; properly, the griffon, or great vulture. See Exodus 19:4; and Note to Obadiah 1:4.

The rendering of the Prayer Book, “like the eagle’s,” follows the Septuagint. The idea that the eagle renewed its youth formed the basis of a Rabbinical story, and no doubt appears also in the myth of the Phoenix. But the psalmist merely refers to the fresh and vigorous appearance of the bird with its new plumage.