By Luke Lancaster
In Paul's first letter to the Corinthians, he uses an image that seems to suggest the Catholic teaching of Purgatory. He says,
According to the commission of God given to me, like a skilled master builder I laid a foundation, and another man is building upon it. Let each man take care how he builds upon it. For no other foundation can any one lay than that which is laid, which is Jesus Christ. Now if any one builds on the foundation with gold, silver, precious stones, wood, hay, stubble—each man’s work will become manifest; for the Day will disclose it, because it will be revealed with fire, and the fire will test what sort of work each one has done. If the work which any man has built on the foundation survives, he will receive a reward. If any man’s work is burned up, he will suffer loss, though he himself will be saved, but only as through fire (1 Cor. 3:10-15).
Paul is giving an analogy for the Corinthian church. He came to the community and spoke about Jesus, converting a number of people and formed a church. They were baptized "into the body" of Christ, and took on His life (1 Cor. 12:13). The works they did after that would be similar to the different types of material used to build houses.
The weak houses that are made out of wood, hay, and stubble would be considered the sins of the people, such as their prideful divisions (1 Cor. 1:10), their jealousy and strife (1 Cor. 3:3), their bad motivations (1 Cor. 4:5), their immorality (1 Cor. 5:1), etc.
Those bad works are contrasted with the good works, which would be houses made out of solid stones, gold, silver, etc. That would be like feeding and supporting Paul and Barnabas (1 Cor. 9:11), imitating Paul's actions (1 Cor. 11:1), love that is patient, kind, and humble (1 Cor. 13:4-5), and faith with hope (1 Cor. 13:13).
At the end of time, when Christ judges mankind of His works (Paul calls this the "Day"), it will be like the man's house will be set on fire. This fire reveals what works he did on earth that were good and bad. What virtues and what vices he had.
Whatever virtues and good works he did will withstand the flames of Christ's judgment, for they will be solid stone, gold, or silver. Whatever vices or sins he did will be burned or purified from his house, such as the flammable wood, hay, or stubble. This judgment at the end of time is similar to Purgatory. The good works will be rewarded in Heaven. The bad works will be purified from the man, for "nothing unclean" shall enter Heaven (Rev. 21:27).
Just as the prophet Malachi spoke of the "refiners fire" in Mal. 3:13, so Paul takes this image and applies it to the end of time (see Kittel's Greek Dictionary of the New Testament, Vol. 6, p. 944). This fire consumes the bad works, which causes the man pain and a loss of rewards. He "suffers loss" from it. In the words of Dr. W. Harold Maher in the Expositors Bible Commentary on 1 Corinthians, the fire either purifies or consumes.
The man who has Christ as His foundation, meaning that He is in a state of grace before God, will still be saved. However, his venial sins are purified from him, and if that causes "suffering," then it is a sort of "punishment" for his evil committed. For fire hurts.
Read more in Pope Benedict XVI's theological work Spe Salvi, specifically paragraph 47.