John Chrysostom

"When the Son of Man shall come in His glory." For now is He come in dishonor, now in affronts and reproaches; but then shall He sit upon the throne of His glory. And continually doth He make mention of glory. For since the cross was near, a thing that seemed to be matter of reproach, for this cause He raises up the hearer; and brings before his sight the judgment seat, and setteth round him all the world. And not in this way only doth He make His discourse awful, but also by showing the Heavens opened. …

Homily on the Gospel of Matthew 79 ↗

Theophylact of Ohrid

Since the first coming of the Lord was not with glory but with dishonor and indignity, He says, "When He shall come in His glory." For at the second coming He will come with glory, escorted by angels.

Commentary on Matthew ↗

Augustine of Hippo

He is now treating of the last judgment, when Christ shall come from heaven to judge the quick and dead. This day of the Divine judgment we call the Last Day, that is, the end of time; for we cannot tell through how many days that judgment will be prolonged; but day, as is the use of holy Scripture, is put for time. …

Catena Aurea by Aquinas ↗

Jerome

But when the Son of Man comes in his glory, and all the angels with him, then he will sit on the throne of his glory. And all the nations will be gathered before him, and he will separate them from one another, as a shepherd separates the sheep from the goats. And he will place the sheep on his right hand, but the goats on the left. …

Commentary on Matthew ↗

Thomas Aquinas

Above, the Lord set forth various parables pertaining to the judgment; but here he treats openly of his own judgment, and he does three things. First, he treats of the coming of the judge; second, of the gathering of those to be judged; third, of the judgment itself. The second is at and all nations shall be gathered together before him; the third at and the king shall say etc. Concerning the first, four things are to be considered. …

Commentary on Matthew ↗