Ps 110:3

Ps 110:3, “Thy people offer themselves willingly In the day of thy power, in holy array: Out of the womb of the morning Thou hast the dew of thy youth.”

Ver. 3. —The subjects of the Priest King are willing soldiers. In accordance with the warlike tone of the whole Psalm, our text describes the subjects as an army. That military metaphor comes out more closely when we attach the true meaning of the words, "in the day of thy power." The word rendered, and rightly rendered, "power," has the same ambiguity which that word has in the English of the date of our translation, and for a century later, as you may find in Shakespeare and Milton, who both used it in the sense of "army". Singularly enough we do not employ "powers" in that meaning, but we do another word which means the same thing—and talk of "forces," meaning thereby "troops" ..." The day of thy power" is not a mere synonym for "the time of thy might," but means specifically "the day of thine army," that is, "the day when thou dost muster thy forces and set them in array for the war". The King is going forth to conquest. But he goes not alone. Behind him come his faithful followers, all pressing on with willing hearts and high courage.

Ver. 3. —In the beauties of holiness. This expression is usually read as if it belonged either to the words immediately preceding, or to those immediately following. But in either case the connection is somewhat difficult and obscure. It seems better regarded as a distinct and separate clause, adding a fresh trait to the description of the army. And what that is we need not find any difficulty in ascertaining. "The beauties of holiness" is a frequent phrase for the sacerdotal garments, the holy festal attire of the priests of the Lord. So considered, how beautifully it comes in here. The conquering King whom the psalm hymns is a Priest for ever; and he is followed by an army of priests. The soldiers are gathered in the day of the muster, with high courage and willing devotion, ready to fling away their lives; but they are clad not in mail, but in priestly robes; like those who wait before the altar rather than like those who plunge into the fight, like those who compassed Jericho with the ark for their standard and the trumpets tor all their weapons. We can scarcely fail to remember the words which echo these and interpret them. "The armies which were in heaven followed him on white horses, clothed in fine linen, white and clean" —a strange armour against sword cut and spear thrust.

Ver. 3. —Thou hast the dew of thy youth. These words are often misunderstood, and taken to be a description of the fresh, youthful energy attributed by the Psalm to the Priest King of this nation of soldier priests. The misunderstanding, I suppose, has led to the common phrase, "the dew of one’s youth". But the reference of the expression is to the army, not to its leader. "Youth" here is a collective noun, equivalent to "young men". The host of his soldier subjects is described as a band of young warriors, whom he leads, in their fresh strength and countless numbers and gleaming beauty like the dew of the morning... It is as a symbol of the refreshing which a weary world will receive from the conquests and presence of the King and his host, that they are likened to the glittering morning dew. Another prophetic Scripture gives us the same emblem when it speaks of Israel being "in the midst of many people as a dew from the Lord". Such ought to be the effect of our presence. We are meant to gladden, to adorn, to refresh this parched, prosaic world, with a freshness brought from the chambers of the sunrise.

The dew, formed, in the silence of the darkness while men sleep, falling as willingly on a bit of dead wood as anywhere, hanging its pearls on every poor spike of grass, and dressing everything on which it lies with strange beauty, each separate globule tiny and evanescent, but each flashing back the light, and each a perfect sphere: feeble one by one, but united mighty to make the pastures of the wilderness rejoice—so, created in silence by an unseen influence, feeble when taken in detail, but strong in their myriads, glad to occupy the lowliest place, and each "bright with something of celestial light," Christian men and women are to be in the midst of many people as a dew from the Lord.

Alexander Maclaren

It seems, the oriental writers delighted to represent the dew as a kind of birth, as the offspring of the morning. And if so, surely there could be no image in the whole compass of the universe better adapted to the psalmist’s purpose, or more strongly significant of those multitudes of proselytes, which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God; by the powerful energy of his word and Spirit. Upon this supposition, the whole verse describes the willing subjection, the gracious accomplishments, and the vast number of Christ’s converts. 

James Hervey (1713-14—1758), in "Meditations and contemplations."