Augustine of Hippo

Compare [John's] other words: "The hour is coming, and now is here, when the dead shall hear the voice of the Son of God, and those who hear shall live"—implying that the rest of the dead (who do not hear) will "not come to life." The added clause, "until the thousand years were finished," means that during that time "the rest of the dead" did "not come to life" as they should by passing over from death to life. Therefore, in the day of the body's resurrection, they will go forth from their tombs, not to life but to "judgment," meaning that condemnation that is called the second death. Anyone at all who will have failed to "come to life" during this millennium, this whole era of the first resurrection, by not hearing "the voice of the Son of God" and by not passing from death to life will certainly, when the second and bodily resurrection comes, pass to the second death, body and soul together.

Anyone who thus participates [in the first resurrection] is one who not only rises from the death of sin but also perseveres in his newfound life. "Over these," says John, "the second death has no power." Therefore, it has power over all the others of whom he said above: "The rest of the dead did not come to life till the thousand years were finished." They may have lived long enough in their bodies, in the period John calls the "thousand years," but they did not rise from the binding death of their ungodliness. If they had, they would have shared in the first resurrection and thus escaped the power of the second death.