Charles H. Spurgeon on Psalms 110:3

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 McLaren.