The Church Fathers on Purgatory and 1 Cor 3:15

St. Augustine

Lord, rebuke me not in Your indignation, nor correct me in your anger…. In this life may You cleanse me and make me such that I have no need of corrective fire, which is for those who are saved, but as if by fire….For it is said, “He shall be saved, but as if by fire” (1 Cor 3:15). And because it is said, “he shall be saved,” little is thought of that fire. Yet, plainly, though we be saved by fire, that fire will be more severe than anything man can suffer in this life. (Explanations of the Psalms 37.3 – Quoted in Jurgens @ 1467)

And it is not impossible that something of the same kind [purification by fire] may take place even after this life. It is a matter that may be inquired into, and either ascertained or left doubtful, whether some believers shall pass through a kind of purgatorial fire, and in proportion as they have loved with more or less devotion the goods that perish, be less or more quickly delivered from it. (Commentary on 1 Cor 3 in the Enchiridion, 69)

St Cyprian

It is one thing, when cast into prison, not to go out thence until one has paid the uttermost farthing; another thing to instantly receive the reward of faith and courage. It is one thing, tortured by long suffering for sins, to be cleansed and long purged as by fire; another to have purged all sins by suffering [martyrdom]. It is one thing, in the end, to be in suspense till the sentence of God at the day of judgment; another to be at once crowned by the Lord(Epistle 51.20 comparing Martyrdom to purgation).

St. Thomas Aquinas

We must therefore say that the very venial sins that insinuate themselves into those who have a care for earthly things, are designated by wood, hay, and stubble. For just as these are stored in a house, without belonging to the substance of the house, and can be burnt, while the house is saved, so also venial sins are multiplied in a man, while the spiritual edifice remains, and for them, man suffers fire, either of temporal trials in this life, or of purgatory after this life, and yet he is saved for ever. (Summa, I, IIae 89.2)

The First Council of Lyons (1245)

… is granted that certain sins….are forgiven in the the future life and, since the Apostle says that, “fire will test the work of each one, of what kind it is,” and “if any man’s work burn he shall suffer loss, but he himself shall be saved, yet so as by fire” (1 Cor 3:13,15),….we indeed, calling it purgatory according to the traditions and authority of the Holy Fathers, wish in the future that it be called by that name. For in that transitory fire certainly sins, though not capital  or criminal,….are cleansed. (Lyon # 23, Denz 456)