Theophylact of Ohrid

He himself will not perish in the same way as his works, that is, he will not pass into nothingness, but will be "saved," that is, preserved whole, so that he may burn in the fire. Among us too, regarding wood that does not easily burn up and turn to ash, it is customary to say that it remains whole in the fire, so that a considerable amount of time is required for its burning. …

Commentary on 1 Corinthians ↗

Gregory the Dialogist

For when St. Paul saith, that Christ is the foundation: and by and by addeth: And if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble: the work of every one, of what kind it is, the fire shall try. If any man's work abide which he built thereupon, he shall receive reward; if any man's work burn, he shall suffer detriment, but himself shall be saved, yet so as by fire. …

Dialogues, Book 4, Chapter 41 ↗

Thomas Aquinas

Secondly, he shows the same thing in regard to evil works, saying: If any man's work burn because of any of the above fires, he shall suffer loss for doing them, but not to the point of damnation; hence he adds: but he himself shall be saved with eternal salvation: "Israel is saved by the Lord with everlasting salvation" (Is 45:17), but only as by fire, which he previously endured either in this life or at the end of the world; hence it says in Ps 66 (v.12): "We went through fire and through water; yet thou hast brought us forth to a …

Commentary on 1 Corinthians ↗

Bonaventure

The purgatorial fire is a corporeal fire, by which nevertheless the spirits of the just, who in this life did not fulfill condign penance and satisfaction, are afflicted to a greater or lesser degree, according as they carried with them from this life more or less of what is combustible. They are afflicted, however, less gravely than in hell, and more gravely than in this world; yet not so gravely that they do not always hope and know that they are not in hell. …

Breviloquium, Part 7 ↗