Thomas Aquinas, Compendium of Theology

We clearly gather from all this, that by the passion and death of Christ and by the glory of His resurrection and ascension, we are freed from sin and death, and have received justice and the glory of immortality, the former in actual fact, the latter in hope. All these events we have mentioned (the passion, the death, the resurrection, and also the ascension) were accomplished in Christ according to His human nature. Therefore we must conclude that Christ has rescued us from spiritual and bodily evils, and has put us in the way of spiritual and eternal goods, by what He suffered or did in His human nature.

He who acquires goods for people also, in consequence, distributes the same to them. But the distribution of goods among many requires judgment, so that each may receive what corresponds to his degree. Therefore Christ, in the human nature in which He has accomplished the mysteries of man's salvation, is fittingly appointed by God to be judge over the men He has saved. We are told that this is so, in John 5:27: "He [the Father] hath given Him [the Son] power to do judgment, because He is the Son of man." There is also another reason. Those who are to be judged ought to see the judge. But the sight of God, in whom the judicial authority resides, in His own proper nature, is the reward that is meted out in the judgment. Hence the men to be judged, the good as well as the wicked, ought to see God as judge, not in His proper nature, but in His assumed nature. If the wicked saw God in His divine nature, they would be receiving the very reward of which they had made themselves unworthy.

Furthermore, the office of judge is a suitable recompense by way of exaltation, corresponding to the humiliation of Christ, who was willing to be humiliated to the point of being unjustly judged by a human judge. To give expression to our belief in this humiliation, we say explicitly in the Creed, that He suffered under Pontius Pilate. Therefore this exalted reward of being appointed by God to judge all men, the living and the dead, in His human nature, was due to Christ, according to Job 36:17: "Thy cause hath been judged as that of the wicked. Cause and judgment Thou shalt recover."

Moreover, since this judicial power pertains to Christ's exaltation, as does the glory of His resurrection, Christ will appear at the judgment, not in humility, which belonged to the time of merit, but in the glorious form that is indicative of His reward. We are assured in the Gospel that "they shall see the Son of man coming in a cloud with great power and majesty" (Luke 21:27). And the sight of His glory will be a joy to the elect who have loved Him; to these is made the promise, in Isaias 33:17, that they "shall see the King in His beauty." But to the wicked this sight will mean confusion and lamentation, for the glory and power of the judge will bring grief and dread to those who fear damnation. We read of this in Isaias 26:11: "Let the envious people see and be confounded, and let fire devour Thy enemies."

Although Christ will show Himself in His glorious form, the marks of the Passion will appear in Him, not with disfigurement, but with beauty and splendor, so that at the sight of them the elect, who will perceive that they have been saved through the sufferings of Christ, will be filled with joy; but sinners, who have scorned so great a benefit, will be filled with dismay. Thus we read in the Apocalypse 1:7: "Every eye shall see Him, and they also that pierced Him. And all the tribes of the earth shall bewail themselves because of Him."