10 “What is man, that You are mindful of him? Or the son of man, that You visit him?”. It may be asked, what distinction there is between man and son of man. For if there were none, it would not be expressed thus, “man, or son of man,” disjunctively. For if it were written thus, “What is man, that You are mindful of him, and son of man, that You visit him?” it might appear to be a repetition of the word “man.” But now when the expression is, “man or son of-man,” a distinction is more clearly intimated.
This is certainly to be remembered, that every son of man is a man; although every man cannot be taken to be a son of man. Adam, for instance, was a man, but not a son of man. Wherefore we may from hence consider and distinguish what is the difference in this place between man and son of man; namely, that they who bear the image of the earthy man, who is not a son of man, should be signified by the name of men; but that they who bear the image of the heavenly Man, should be rather called sons of men; for the former again is called the old man and the latter the new; but the new is born of the old, since spiritual regeneration is begun by a change of an earthy, and worldly life; and therefore the latter is called son of man.
“Man” then in this place is earthy, but “son of man” heavenly; and the former is far removed from God, but the latter present with God; and therefore is He mindful of the former, as in far distance from Him; but the latter He visits, with whom being present He enlightens him with His countenance. For “salvation is far from sinners;” and, “The light of Your countenance has been stamped upon us, O Lord.” So in another Psalm he says, that men in conjunction with beasts are made whole together with these beasts, not by any present inward illumination, but by the multiplication of the mercy of God, whereby His goodness reaches even to the lowest things; for the wholeness of carnal men is carnal, as of the beasts; but separating the sons of men from those whom being men he joined with cattle, he proclaims that they are made blessed, after a far more exalted method, by the enlightening of the truth itself, and by a certain inundation of the fountain of life.
For he speaks thus: “Men and beasts You will make whole, O Lord, as Your mercy has been multiplied, O God. But the sons of men shall put their trust in the covering of Your wings. They shall be inebriated with the richness of Your house, and of the torrent of Your pleasures You shall make them drink. For with You is the fountain of life, and in Your light shall we see light. Extend Your mercy to them that know You.” Through the multiplication of mercy then He is mindful of man, as of beasts; for that multiplied mercy reaches even to them that are afar off; but He visits the son of man, over whom, placed under the covering of His wings, He extends mercy, and in His light gives light, and makes him drink of His pleasures, and inebriates him with the richness of His house, to forget the sorrows and the wanderings of his former conversation.
This son of man, that is, the new man, the repentance of the old man begets with pain and tears. He, though new, is nevertheless called yet carnal, while he is fed with milk; “I would not speak unto you as unto spiritual, but as unto carnal,” says the Apostle. And to show that they were already regenerate, he says, “As unto babes in Christ, I have given you milk to drink, not meat.” And when he relapses, as often happens, to the old life, he hears in reproof that he is a man; “Are ye not men,” he says, “and walk as men?”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)