Genesis 3:22

As one of us. — See Note on Genesis 1:26. By the fall man had sunk morally, but grown mentally. He had asserted his independence, had exercised the right of choosing for himself, and had attained to a knowledge without which his endowment of free-will would have remained in abeyance. There is something painful and humiliating in the idea of Chrysostom and other Fathers that the Deity was speaking ironically, or even with insult (Augustine). All those qualities which constitute man’s likeness to God — free-will, self-dependence, the exercise of reason and of choice — had been developed by the fall, and Adam was now a very different being from what he had been in the days of his simple innocency.

Lest he put forth his hand. — Adam had exercised the power of marring God’s work, and if an unending physical life were added to the gift of freewill now in revolt against God, his condition and that of mankind would become most miserable. Man is still to attain to immortality, but it must now be through struggle, sorrow, penitence, faith, and death. Hence a paradise is no fit home for him. The Divine mercy, therefore, commands Adam to quit it, in order that he may live under conditions better suited for his moral and spiritual good.