12 Let it not by any means surprise any one that He says, “My judgment is true; because I am not alone, but I and the Father that sent me;” while He has said in another place, “The Father judges not any man, but all judgment has He given to the Son.” We have already discoursed on these same words of the evangelist, and we remind you now that this was not said because the Father will not be with the Son when He comes to judge, but because the Son alone will be apparent to the good and the bad in the judgment, in that form in which He suffered, and rose again, and ascended into heaven. For at that moment, indeed, as they were beholding Him ascending, the angelic voice sounded in the ears of His disciples, “So shall He come in like manner as you have seen Him going into heaven;” that is, in the form of man in which He was judged, will He judge, in order that also that prophetic utterance may be fulfilled, “They shall look upon Him whom they pierced.” But when the righteous go into eternal life, we shall see Him as He is; that will not be the judgment of the living and the dead, but only the reward of the living.
Source: Tractates on the Gospel of John (New Advent)