3 “Whoso hears my words,” says He, “and believes Him that sent me, has eternal life, and shall not come into judgment, but is passed from death unto life.” Where, when do we come from death to life, that we come not into judgment? In this life there is a passing from death to life; in this life, which is not yet life, there is a passing hence from death unto life. What is that passing? “Whoso hears my words,” He said, “and believes Him that sent me.” Observing these, you believe and passest.
And does a man pass while standing? Evidently; for in body he stands, in mind he passes. Where was he, whence he should pass, and whither does he pass? He passes from death to life. Look at a man standing, in whom all that is here said may happen. He stands, he hears, perhaps he did not believe, by hearing he believes: a little before he did not believe, just now he believes; he has made a passage, as it were, from the region of unbelief to the region of faith, by motion of the heart, not of the body, by a motion into the better; because they who again abandon faith move into the worse.
Behold, in this life, which, just as I have said, is not yet life, there is a passing from death to life, so that there may not be a coming into judgment. But why did I say that it is not yet life? If this were life, the Lord would not have said to a certain man, “If you will come into life, keep the commandments.” For He says not to him, If you will come into eternal life; He did not add eternal, but said only life. Therefore this life is not to be named life, because it is not a true life.
What is true life, but that which is eternal life? Hear the apostle speaking to Timothy, when he says, “Charge them that are rich in this world, not to be high-minded, nor to trust in uncertain riches, but in the living God, who gives us all things richly to enjoy; let them do good, be rich in good works, ready to distribute, to communicate.” Why does he say this? Hear what follows: “Let them lay up in store for themselves a good foundation for the time to come, that they may lay hold of the true life.” If they ought to lay up for themselves a good foundation for the time to come, in order to lay hold of the true life, surely this in which they were is a false life.
For why should you desire to lay hold of the true, if you have the true already? Is the true to be laid hold of? There must then be a departing from the false. And by what way must be the departing? Whither? Hear, believe; and you make the passage from death into life, and comest not into judgment.
Source: Tractates on the Gospel of John (New Advent)