7 Himself explains that already, and goes on, “Verily, verily, I say unto you.” In case, because He said “is passed from death to life,” we should understand this of the future resurrection, and willing to show that he who believes is passed, and that to pass from death to life is to pass from unbelief to faith, from injustice to justice, from pride to humility, from hatred to charity, He says now, “Verily, verily, I say unto you, The hour comes, and now is.” What more evident? “And now is, when the dead shall hear the voice of the Son of God, and they that hear shall live.” We have already spoken of these dead. What think we, my brethren? Are there no dead in this crowd that hear me? They who believe and act according to the true faith do live, and are not dead. But they who either do not believe, or believe as the devils believe, trembling, and living wickedly, confessing the Son of God, and without charity, must rather be esteemed dead. This hour, however, is still passing. For the hour of which the Lord spoke will not be an hour of the twelve hours of a day. From the time when He spoke even to the present, and even to the end of the world, the same one hour is passing; of which hour John says in his epistle, “Little children, it is the last hour.” Therefore, is now. Whoso is alive, let him live; whoso was dead, let him live; let him hear the voice of the Son of God, who lay dead; let him arise and live. The Lord cried out at the sepulchre of Lazarus, and he that was four days dead arose. He who stank in the grave came forth into the air. He was buried, a stone was laid over him: the voice of the Saviour burst asunder the hardness of the stone; and your heart is so hard, that Divine Voice does not yet break it! Rise in your heart; go forth from your tomb. For you were lying dead in your heart as in a tomb, and pressed down by the weight of evil habit as by a stone. Rise, and go forth. What is Rise, and go forth? Believe and confess. For he that has believed has risen; he that confesses is gone forth. Why said we that he who confesses is gone forth? Because he was hid before confessing; but when he does confess, he goes forth from darkness to light. And after he has confessed, what is said to the servants? What was said beside the corpse of Lazarus? “Loose him, and let him go.” How? As it was said to His servants the apostles, “What things you shall loose on earth, shall be loosed in heaven.”
8. “The hour comes, and now is, when the dead shall hear the voice of the Son of God; and they that hear shall live.” From what source shall they live? From life. From what life? From Christ. How do we prove that the source is Christ the life? “I am,” says He, “the way, the truth, and the life.” Do you wish to walk? “I am the way.” Do you wish not to be deceived? “I am the truth.” Would you not die? “I am the life.” This says your Saviour to you: There is not whither you may go but to me; there is not whereby you may go but by me. Therefore this hour is going on now, this act is clearly taking place, and does not at all cease. Men who were dead, rise; they pass over to life; at the voice of the Son of God they live; from Him they live, while persevering in the faith of Him. For the Son has life, whence He has it that they that believe shall live.
Source: Tractates on the Gospel of John (New Advent)