15 He has finished speaking of the resurrection of souls; it remains to speak more evidently of the resurrection of bodies. “And has given Him authority also to execute judgment:” not only to raise up souls by faith and wisdom, but also to execute judgment. But why this? “Because He is the Son of man.” Therefore the Father does something through the Son of man, which He does not from His own substance, to which the Son is equal: as, for instance, that He should be born, crucified, dead, and have a resurrection; for not any of these is contingent to the Father.
In the same manner also the raising again of bodies. For the raising to life of souls the Father effects from His own substance, by the substance of the Son, in which the Son is equal to Him; because souls are made partakers of that unchangeable light, but not bodies; but the raising again of bodies, the Father effects through the Son of man. For “He has given Him authority also to execute judgment, because He is the Son of man;” according to that which He said above, “For the Father judges not any man.”
And to show that He said this of the resurrection of bodies, He goes on: “Marvel not at this, for the hour comes:” not, and now is; but, “the hour comes, in which all that are in the graves (this you have already heard sufficiently explained yesterday) shall hear His voice, and come forth.” Where? Into judgment: “They that have done well, into the resurrection of life; and they that have done evil, into the resurrection of judgment.” And dost Thou do this alone, because the Father has given all judgment to the Son, and judges not any man?
I, says He, do it. But how doest Thou it? “I cannot of myself do anything; as I hear, I judge; and my judgment is just.” When He was treating of the resurrection of souls, He did not say, I hear; but, I see. For I hear refers to the command of the Father as giving order. Therefore, now as a man, just as He than whom the Father is greater; as from the form of a servant, not from the form of God, “As I hear, I judge; and my judgment is just.” Whence is the man's judgment a just one? My brethren, mark well: “Because I seek not my own will, but the will of Him that sent me.”
Source: Tractates on the Gospel of John (New Advent)