Objection 1. It would seem that at the judgment Christ will not appear in His glorified humanity. For a gloss [St. Augustine, Tract. cxx in Joan.] on John 19:37, "They shall look on him whom they pierced," says: "Because He will come in the flesh wherein He was crucified." Now He was crucified in the form of weakness. Therefore He will appear in the form of weakness and not in the form of glory.
Objection 2. Further, it is stated (Matthew 24:30) that "the sign of the Son of man shall appear in heaven," namely, "the sign of the cross," as Chrysostom says (Hom. lxxvii in Matth.), for "Christ when coming to the judgment will show not only the scars of His wounds but even His most shameful death." Therefore it seems that He will not appear in the form of glory.
Objection 3. Further, Christ will appear at the judgment under that form which can be gazed upon by all. Now Christ will not be visible to all, good and wicked, under the form of His glorified humanity: because the eye that is not glorified is seemingly unproportionate to see the clarity of a glorified body. Therefore He will not appear under a glorified form.
Objection 4. Further, that which is promised as a reward to the righteous is not granted to the unrighteous. Now it is promised as a reward to the righteous that they shall see the glory of His humanity (John 10:9): "He shall go in, and go out, and shall find pastures, i.e. refreshment in His Godhead and humanity," according to the commentary of Augustine [De Spiritu et Anima, work of an unknown author. St. Thomas, De Anima, ascribes it to Alcherus, a Cistercian monk; see above 70, 2, ad 1 and Isaiah 33:17: "His eyes shall see the King in his beauty." Therefore He will not appear to all in His glorified form.
Objection 5. Further, Christ will judge in the form wherein He was judged: wherefore a gloss [St. Augustine, Tract. xix, in Joan.] on John 5:21, "So the Son also giveth life to whom He will," says: "He will judge justly in the form wherein He was judged unjustly, that He may be visible to the wicked." Now He was judged in the form of weakness. Therefore He will appear in the same form at the judgment.
On the contrary, It is written (Luke 21:27): "Then they shall see the Son of man coming in a cloud with great power and majesty." Now majesty and power pertain to glory. Therefore He will appear in the form of glory.
Further, he who judges should be more conspicuous than those who are judged. Now the elect who will be judged by Christ will have a glorified body. Much more therefore will the Judge appear in a glorified form.
Further, as to be judged pertains to weakness, so to judge pertains to authority and glory. Now at His first coming when Christ came to be judged, He appeared in the form of weakness. Therefore at the second coming, when He will come to judge, He will appear in the form of glory.
I answer that, Christ is called the mediator of God and men (1 Timothy 2:5) inasmuch as He satisfies for men and intercedes for them to the Father, and confers on men things which belong to the Father, according to John 17:22, "The glory which Thou hast given Me, I have given to them." Accordingly then both these things belong to Him in that He communicates with both extremes: for in that He communicates with men, He takes their part with the Father, and in that He communicates with the Father, He bestows the Father's gifts on men. Since then at His first coming He came in order to make satisfaction for us to the Father, He came in the form of our weakness. But since at His second coming He will come in order to execute the Father's justice on men, He will have to show forth His glory which is in Him by reason of His communication with the Father: and therefore He will appear in the form of glory.
Reply to Objection 1. He will appear in the same flesh, but not under the same form.
Reply to Objection 2. The sign of the cross will appear at the judgment, to denote not a present but a past weakness: so as to show how justly those were condemned who scorned so great mercy, especially those who persecuted Christ unjustly. The scars which will appear in His body will not be due to weakness, but will indicate the exceeding power whereby Christ overcame His enemies by His Passion and infirmity. He will also show forth His most shameful death, not by bringing it sensibly before the eye, as though He suffered it there; but by the things which will appear then, namely the signs of His past Passion, He will recall men to the thought of His past death.
Reply to Objection 3. A glorified body has it in its power to show itself or not to show itself to an eye that is not glorified, as stated above (85, 2, ad 3). Hence Christ will be visible to all in His glorified form.
Reply to Objection 4. Even as our friend's glory gives us pleasure, so the glory and power of one we hate is most displeasing to us. Hence as the sight of the glory of Christ's humanity will be a reward to the righteous, so will it be a torment to Christ's enemies: wherefore it is written (Isaiah 26:11): "Let the envious people see and be confounded and let fire" (i.e. envy) "devour Thy enemies."
Reply to Objection 5. Form is taken there for human nature wherein He was judged and likewise will judge; but not for a quality of nature, namely of weakness, which will not be the same in Him when judging as when judged (Cf. ad 2).
Source: Summa Theologica (New Advent)