Who satisfieth thy mouth with good things - The word translated "thy mouth" here is rendered in the Chaldee "thy age;" in the Arabic, the Septuagint, and the Latin Vulgate, "thy desire;" in the Syriac, "thy body;" DeWette renders it, "thy age." So also Tholuck. The Hebrew word - עדי ‛ădı̂y - is rendered "ornaments" in Exodus 33:4-6; 2-Samuel 1:24; Isaiah 49:18; Jeremiah 2:32; Jeremiah 4:30; Ezekiel 7:20; Ezekiel 16:11, Ezekiel 16:17 (margin,); Ezekiel 23:40; and "mouth" in Psalm 32:9, as here. These are the only places in which it occurs. Gesenius renders it here "age," and supposes that it stands in contrast with the word "youth" in the other part of the verse. The connection would seem to demand this, though it is difficult to make it out from any usage of the Hebrew word. Professor Alexander renders it "thy soul" - from the supposition that the Hebrew word "ornament" is used as if in reference to the idea that the "soul" is the chief glory or ornament of man. This seems, however, to be a very forced explanation. I confess myself unable to determine the meaning.
So that thy youth is renewed like the eagle's - Compare Isaiah 40:31. The allusion, to which there is supposed to be a reference here, is explained in the notes at that passage. Whatever may be true in regard to the supposed fact pertaining to the eagle, about its renewing its strength and vigor in old age, the meaning here is simply that the strength of the psalmist in old age became like the strength of the eagle. Sustained by the bounty of God in his old age he became, as it were, young again.

Who satisfieth thy mouth -
5. For continual communications of spiritual and temporal good; so that the vigor of his mind was constantly supported and increased.
Thy youth is renewed like the eagle's - There is such a vast variety of the eagle, or genus Falco, that it is not easy to determine which is meant here.
The Hebrew נשר neser is a general name for such as were known in the land of Judea; which were probably such as belong to the genus Aquila, comprehending forty-one species and seven varieties.
There are as many legends of the eagle among the ancient writers, as there are of some saints in the calendar; and all equally true. Even among modern divines, Bible Dictionary men, and such like, the most ridiculous tales concerning this bird continue to be propagated; and no small portion of them have been crowded into comments on this very verse. One specimen my old Psalter affords, which, for its curiosity, I shall lay before the reader: -
Trans. Newed sal be als of aeren thi youthed.
Par - The arne when he is greved with grete elde, his neb waxis so gretely, that he may nogt open his mouth and take mete: bot then he smytes his neb to the stane, and has away the solgh, and than he gaes til mete, and be commes yong a gayne. Swa Criste duse a way fra us oure elde of syn and mortalite, that settes us to ete oure brede in hevene, and newes us in hym.
The plain English of all this is: -
"When the arne [eagle, from the Anglo-Saxon a word which Dr. Jamieson has not entered in his dictionary] is oppressed with old age, his bill grows so much that he cannot open his mouth in order to take meat. He then smites his bill against a stone, and breaks off the slough - the excrescence that prevented him from eating; and then he goes to his ordinary food, and becomes young again. So Christ takes away from us our old age of sin and death, and gives us to eat of that bread which comes down from heaven: and thus gives us a new life in himself."
I believe the meaning of the psalmist is much more simple: he refers to the moulting of birds, which, in most, takes place annually, in which they cast their old feathers and get a new plumage. To express this, he might as well have chosen any bird, as this is common to all the feathered race; but he chose the king of the birds, because of his bulk, his strength, and vivacity.
The long life of the eagle might have induced the psalmist to give it the preference. An eagle was nine years in the possession of Owen Holland, Esq., of Conway, in Wales, and had lived thirty-two years in the possession of the gentleman who made it a present to him: but of its previous age, for it came from Ireland, we are not informed. Keysler relates that an eagle died at Vienna, after a confinement of one hundred and four years!
The eagle can subsist a long time without food. That first mentioned above, through the neglect of a servant, was twenty-one days without food, and yet survived this long fast.
The meaning and moral of the psalmist are not difficult of comprehension. The Israelites, when redeemed from their captivity, should be so blessed by their God that they should reacquire their political strength and vigor; and should be so quickened by the Divine Spirit, that old things should be passed away, and all things become new.

Who satisfieth thy mouth with good [things; so that] thy (d) youth is renewed like the eagle's.
(d) As the eagle, when her beak overgrows, sucks blood and so is renewed in strength, even so God miraculously gives strength to his Church above all man's expectations.

Who satisfieth thy mouth with good things,.... With the good things in the heart of God, with his favour and lovingkindness, as with marrow and fatness; with the good things in the hands of Christ, with the fulness of grace in him, with pardon, righteousness, and salvation by him; with the good things of the Spirit of God, his gifts and graces; and with the provisions of the Lord's house, the goodness and fatness of it; these he shows unto his people, creates hungerings and thirstings in them after them, sets their hearts a longing after them, and then fills and satisfies them with them: hence the Septuagint, Vulgate Latin, and Arabic versions render it, "who filleth thy desire with good things": the word used has sometimes the signification of an ornament; wherefore Aben Ezra interprets it of the soul, which is the glory and ornament of the body, and renders it, "who satisfieth thy soul with good things"; which is not amiss: "so that thy youth is renewed like the eagle's"; not the youth of the body, or the juvenile vigour of it; nor the outward prosperity of it; but the youth of grace, or a renewal of spiritual love and affection to divine and heavenly persons and things; of holy zeal for God, his ways and worship; for Christ, his Gospel, truths, and ordinances; of spiritual joy and comfort, strength, liveliness, and activity, as formerly were in the days of espousals, in the youth of first conversion, or when first made acquainted with the best things; so that though the outward man may decay, yet the inward man is renewed day by day: and this is said to be "like the eagle's", whose youth and strength are renewed, as some observe (a), by dropping their feathers, and having new ones, by feeding upon the blood of slain creatures; and whereas, when they are grown old, the upper part of their bill grows over the lower part (b), so that they are not able, to eat, but must die through want; Austin (c) says, that by rubbing it against a rock, it comes to its use of eating, and so recovers its strength: but there is no need to have recourse to any of these things; for as the old age of au eagle is lively and vigorous, like the youth of another creature; so it is here signified, that saints through the grace of God, even in old age, become fat and flourishing, and fruitful, and are steadfast and immovable, always abounding in the work of the Lord, run and are not weary, walk and faint not, Isaiah 40:31, all which are inestimable mercies, and the Lord is to be praised for them.
(a) Ambrosii Opera, tom. 5. p. 78. (b) Aristot. de Animal. l. 9. c. 32. Plin. Nat. Hist. l. 10. c. 3. (c) Opera, tom. 8. in Psal. 102. fol. 474. c.

By God's provision, the saint retains a youthful vigor like the eagles (Psalm 92:14; compare Isaiah 40:31).

The eagles - Which lives long in great strength and vigour.