While reading a bit of William Barclay, I happened upon his thoughts on Universalism, which referred back to Gregory of Nyssa, a 4th-5th century theologian, and one of great renown. Barclay writes,
Gregory of Nyssa offered three reasons why he believed in universalism.
First, he believed in it because of the character of God. “Being good, God entertains pity for fallen man; being wise, he is not ignorant of the means for his recovery.”
Second, he believed in it because of the nature of evil. Evil must in the end be moved out of existence, “so that the absolutely non-existent should cease to be at all.” Evil is essentially negative and doomed to non-existence.
Third, he believed in it because of the purpose of punishment. The purpose of punishment is always remedial. Its aim is “to get the good separated from the evil and to attract it into the communion of blessedness.”
Punishment will hurt, but it is like the fire which separates the alloy from the gold; it is like the surgery which removes the diseased thing; it is like the cautery which burns out that which cannot be removed any other way.
So, I am trying to pin down a few of those quotes from Gregory:
Then it seems, I said, that it is not punishment chiefly and principally that the Deity, as Judge, afflicts sinners with; but He operates, as your argument has shown, only to get the good separated from the evil and to attract it into the communion of blessedness.
That, said the Teacher, is my meaning; and also that the agony will be measured by the amount of evil there is in each individual. For it would not be reasonable to think that the man who has remained so long as we have supposed in evil known to be forbidden, and the man who has fallen only into moderate sins, should be tortured to the same amount in the judgment upon their vicious habit; but according to the quantity of material will be the longer or shorter time that that agonizing flame will be burning; that is, as long as there is fuel to feed it. In the case of the man who has acquired a heavy weight of material, the consuming fire must necessarily be very searching; but where that which the fire has to feed upon has spread less far, there the penetrating fierceness of the punishment is mitigated, so far as the subject itself, in the amount of its evil, is diminished. In any and every case evil must be removed out of existence, so that, as we said above, the absolutely non-existent should cease to be at all. Since it is not in its nature that evil should exist outside the will, does it not follow that when it shall be that every will rests in God, evil will be reduced to complete annihilation, owing to no receptacle being left for it?
But, said I, what help can one find in this devout hope, when one considers the greatness of the evil in undergoing torture even for a single year; and if that intolerable anguish be prolonged for the interval of an age, what grain of comfort is left from any subsequent expectation to him whose purgation is thus commensurate with an entire age? (Gregory of Nyssa: Philosophical Works: On the Soul and the Resurrection)
I find the highlighted area noticable for a reason. During the time of Christ and there afterwards, the Jews taught that the fire of hells burned the unrepentant soul for 12 months. Is Gregory referring to that time period here?
In the same way when death, and corruption, and darkness, and every other offshoot of evil had grown into the nature of the author of evil, the approach of the Divine power, acting like fire1 , and making that unnatural accretion to disappear, thus by purgation2 of the evil becomes a blessing to that nature, though the separation is agonizing. Therefore even the adversary himself will not be likely to dispute that what took place was both just and salutary, that is, if he shall have attained to a perception of the boon. For it is now as with those who for their cure are subjected to the knife and the cautery; they are angry with the doctors, and wince with the pain of the incision; but if recovery of health be the result of this treatment, and the pain of the cautery passes away, they will feel grateful to those who have wrought this cure upon them. In like manner, when, after long periods of time, the evil of our nature, which now is mixed up with it and has grown with its growth, has been expelled, and when there has been a restoration of those who are now lying in Sin to their primal state, a harmony of thanksgiving will arise from all creation3 , as well from those who in the process of the purgation have suffered chastisement, as from those who needed not any purgation at all. These and the like benefits the great mystery of the Divine incarnation bestows. For in those points in which He was mingled with humanity, passing as He did through all the accidents proper to human nature, such as birth, rearing, growing up, and advancing even to the taste of death, He accomplished all the results before mentioned, freeing both man from evil, and healing even the introducer of evil himself. For the chastisement, however painful, of moral disease is a healing of its weakness. (Gregory of Nyssa: Apologetic Works: The Great Catechism)
Here is an older work on the subject.