I answer that, Chrysostom (Hom. xxxix in Joan.) seems to think that judiciary power belongs to Christ not as man, but only as God. Accordingly he thus explains the passage just quoted from John: "'He gave Him power to do judgment, because He is the Son of man: wonder not at this.' For He received judiciary power, not because He is man; but because He is the Son of the ineffable God, therefore is He judge. But since the expressions used were greater than those appertaining to man, He said in explanation: 'Wonder not at this, because He is the Son of man, for He is likewise the Son of God.'" And he proves this by the effect of the Resurrection: wherefore He adds: "Because the hour cometh when the dead in their graves shall hear the voice of the Son of God."
But it must be observed that although the primary authority of judging rests with God, nevertheless the power to judge is committed to men with regard to those subject to their jurisdiction. Hence it is written (Dt. 1:16): "Judge that which is just"; and further on (Dt. 1:17): "Because it is the judgment of God," that is to say, it is by His authority that you judge. Now it was said before (Question [8], Articles [1],4) that Christ even in His human nature is Head of the entire Church, and that God has "put all things under His feet." Consequently, it belongs to Him, even according to His human nature, to exercise judiciary power. on this account. it seems that the authority of Scripture quoted above must be interpreted thus: "He gave Him power to do judgment, because He is the Son of Man"; not on account of the condition of His nature, for thus all men would have this kind of power, as Chrysostom objects (Hom. xxxix in Joan.); but because this belongs to the grace of the Head, which Christ received in His human nature.
Now judiciary power belongs to Christ in this way according to His human nature on three accounts. First, because of His likeness and kinship with men; for, as God works through intermediary causes, as being closer to the effects, so He judges men through the Man Christ, that His judgment may be sweeter to men. Hence (Heb. 4:15) the Apostle says: "For we have not a high-priest, who cannot have compassion on our infirmities; but one tempted in all things like as we are, without sin. Let us go therefore with confidence to the throne of His grace." Secondly, because at the last judgment, as Augustine says (Tract. xix in Joan.), "there will be a resurrection of dead bodies, which God will raise up through the Son of Man"; just as by "the same Christ He raises souls," inasmuch as "He is the Son of God." Thirdly, because, as Augustine observes (De Verb. Dom., Serm. cxxvii): "It was but right that those who were to be judged should see their judge. But those to be judged were the good and the bad. It follows that the form of a servant should be shown in the judgment to both good and wicked, while the form of God should be kept for the good alone."