11 He endured death, then; but death He hanged on the cross, and mortal men are delivered from death. The Lord calls to mind a great matter, which was done in a figure with them of old: “And as Moses,” says He, “lifted up the serpent in the wilderness, so must the Son of man be lifted up; that every one who believes in Him may not perish, but have everlasting life.” A great mystery is here, as they who read know. Again, let them hear, as well they who have not read as they who have forgotten what perhaps they had heard or read. The people Israel were fallen helplessly in the wilderness by the bite of serpents; they suffered a great calamity by many deaths: for it was the stroke of God correcting and scourging them that He might instruct them. In this was shown a great mystery, the figure of a thing to come: the Lord Himself testifies in this passage, so that no man can give another interpretation than that which the truth indicates concerning itself. Now Moses was ordered by the Lord to make a brazen serpent, and to raise it on a pole in the wilderness, and to admonish the people Israel, that, when any had been bitten by a serpent, he should look to that serpent raised up on the pole. This was done: men were bitten; they looked and were healed. What are the biting serpents? Sins, from the mortality of the flesh. What is the serpent lifted up? The Lord's death on the cross. For as death came by the serpent, it was figured by the image of a serpent. The serpent's bite was deadly, the Lord's death is life-giving. A serpent is gazed on that the serpent may have no power. What is this? A death is gazed on, that death may have no power. But whose death? The death of life: if it may be said, the death of life; ay, for it may be said, but said wonderfully. But should it not be spoken, seeing it was a thing to be done? Shall I hesitate to utter that which the Lord has deigned to do for me? Is not Christ the life? And yet Christ hung on the cross. Is not Christ life? And yet Christ was dead. But in Christ's death, death died. Life dead slew death; the fullness of life swallowed up death; death was absorbed in the body of Christ. So also shall we say in the resurrection, when now triumphant we shall sing, “Where, O death, is your contest? Where, O death, is your sting?” Meanwhile brethren, that we may be healed from sin, let us now gaze on Christ crucified; for “as Moses,” says He, “lifted up the serpent in the wilderness, so must the Son of man be lifted up; that whosoever believes in Him may not perish, but have everlasting life.” Just as they who looked on that serpent perished not by the serpent's bites, so they who look in faith on Christ's death are healed from the bites of sins. But those were healed from death to temporal life; while here He says, “that they may have everlasting life.” Now there is this difference between the figurative image and the real thing: the figure procured temporal life; the reality, of which that was the figure, procures eternal life.
12. “For God sent not His Son into the world to judge the world, but that the world through Him may be saved.” So far, then, as it lies in the physician, He has come to heal the sick. He that will not observe the orders of the physician destroys himself. He has come a Saviour to the world: why is he called the Saviour of the world, but that He has come to save the world, not to judge the world? You will not be saved by Him; you shall be judged of yourself. And why do I say, “shall be judged”? See what He says: “He that believes in Him is not judged, but he that believes not.” What do you expect He is going to say, but “is judged”? “Already,” says He, “has been judged.” The judgment has not yet appeared, but already it has taken place. For the Lord knows them that are His: He knows who are persevering for the crown, and who for the flame; knows the wheat on His threshing-floor, and knows the chaff; knows the good grain, and knows the tares. He that believes not is already judged. Why judged? “Because he has not believed in the name of the only-begotten Son of God.”
13. “And this is the judgment, that light has come into the world, and men loved darkness rather than light, because their deeds were evil.” My brethren, whose works does the Lord find to be good? The works of none: He finds the works of all evil. How is it, then, that some have done the truth, and have come to the light? For this is what follows: “But he that does truth comes to the light, that his deeds may be made manifest, that they are wrought in God.” In what way have some done a good work to come to the light, namely, to Christ? And how have some loved darkness? For if He finds all men sinners, and heals all of sin, and that serpent in which the Lord's death was figured healed them that were bitten, and on account of the serpent's bite the serpent was set up, namely, the Lord's death on account of mortal men, whom He finds unrighteous; how are we to understand that “this is the judgment, that light has come into the world, and men loved darkness rather than light, because their deeds were evil”? How is this? Whose works, in fact, are good? Have You not come to justify the ungodly? “But they loved,” says He, “darkness rather than light.” There He laid the emphasis: for many loved their sins; many confessed their sins; and he who confesses his sins, and accuses them, does now work with God. God accuses your sins: and if you also accuse, you are united to God. There are, as it were, two things, man and sinner. That you are called man, is God's doing; that you are called sinner, is man's own doing. Blot out what you have done, that God may save what He has done. It behooves you to hate your own work in you, and to love the work of God in you. And when your own deeds will begin to displease you, from that time your good works begin, as you find fault with your evil works. The confession of evil works is the beginning of good works. You do the truth, and come to the light. How is it you do the truth? Thou dost not caress, nor soothe, nor flatter yourself; nor say, “I am righteous,” while you are unrighteous: thus, you begin to do the truth. You come to the light, that your works may be made manifest that they are wrought in God; for your sin, the very thing that has given you displeasure, would not have displeased you, if God did not shine into you, and His truth show it you. But he that loves his sins, even after being admonished, hates the light admonishing him, and flees from it, that his works which he loves may not be proved to be evil. But he that does truth accuses his evil works in himself, spares not himself, forgives not himself, that God may forgive him: for that which he desires God to forgive, he himself acknowledges, and he comes to the light; to which he is thankful for showing him what he should hate in himself. He says to God, “Turn away Your face from my sins:” yet with what countenance says it, unless he adds, “For I acknowledge mine iniquity, and my sin is ever before me?” Be that before yourself which you desire not to be before God. But if you will put your sin behind you, God will thrust it back before your eyes; and this He will do at a time when there will be no more fruit of repentance.
Source: Tractates on the Gospel of John (New Advent)