10 What then? How do we understand these two resurrections? Do we, it may be, understand that they who rise now will not rise then; that the resurrection of some is now, of some others then? It is not so. For we have risen in this resurrection, if we have rightly believed; and we ourselves, who have already risen, are looking for another resurrection in the end. Moreover, both now are we risen to eternal life, if we perseveringly continue in the same faith; and then, too, we shall rise to eternal life, when we shall be made equal with the angels. But let Himself distinguish and open up what we have made bold to speak; how there happens to be a resurrection before a resurrection, not of different but of the same persons; nor like that of Lazarus, but into eternal life.
He will open it clearly. Hear ye the Master, while dawning upon us, and as our Sun gliding in upon our hearts; not such as the eyes of flesh desire to look upon, but on whom the eyes of the heart fervently long to be opened. To Him, then, let us give ear: “Verily, verily, I say unto you, The hour comes, and now is, when the dead”— you see that a resurrection is asserted— “shall hear the voice of the Son of God; and they that hear shall live.” Why has He added, “they that hear shall live”?
Why, could they hear unless they lived? It would have been enough, then, to say, “The hour comes, and now is, when the dead shall hear the voice of the Son of God.” We should immediately understand them to be living, since they could not hear unless they lived. No, says He, not because they live they hear; but by hearing they come to life again: “Shall hear, and they that hear shall live.” What, then, is “shall hear,” but “shall obey”? For, as to the hearing of the ear, not all who hear shall live.
Many, indeed, hear and do not believe; by hearing and not believing, they obey not; by not obeying, they live not. And so here, they that “shall hear” are they that “shall obey.” They that obey, then, shall live: let them be sure and certain of it, shall live. Christ, the Word of God, is preached to us; the Son of God, by whom all things were made, who, for the dispensation's sake, surely took flesh, was born of a virgin, was an infant in the flesh, a young man in the flesh, suffering in the flesh, dying in the flesh, rising again in the flesh, ascending in the flesh, promising a resurrection to the flesh, promising a resurrection to the mind— to the mind before the flesh, to the flesh after the mind.
Whoso hears and obeys, shall live; whoso hears and obeys not, that is, hears and despises, hears and believes not, shall not live. Why shall not live? Because he hears not. What is “hears not”? Obeys not. Thus, then, “they that hear shall live.”
Source: Tractates on the Gospel of John (New Advent)