And he will separate them one from another as a shepherd separates the sheep from the goats. (Matt 25:32)
So then people on earth are intermingled, and not only intermingled in that the righteous live side by side with the wicked but they are also indistinguishable.
Between the righteous and the wicked there is no apparent difference. Even as in wintertime you cannot tell the healthy trees apart from the withered tress but in beautiful springtime you can tell the difference, so too each person according to his faith and his works will be exposed.
The wicked will not have any leaves or show any fruit, but the righteous will be clothed with the leaves of eternal life and adorned with the fruit of glory. In this way they will be separated by the heavenly shepherd and Lord.
The earthly shepherd separates animals by their type of body, whereas Christ separates people by their type of soul. The sheep signify righteous people by reason of their gentleness, because they harm no one, and by reason of their patience, because when they are harmed by others they bear it without resistance.
He refers to sinners as goats, however, because these vices characterize goats: capriciousness toward other animals, pride and belligerence.
From a Homily, Incomplete Work on Matthew
