When explaining this question, I like to begin by explaining the concept of Purgatory. The Catechism does this in an approachable way: "All who die in God's grace, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven" (1030).
Purgatory, then, is a place where a person who dies in the friendship of God but still needs to be purified from sin so they can enter Heaven.
Purgatory is substantiated in Scripture. In Second Maccabees, the aftermath of a battle is described in which the soldiers of Israel who perished in the fighting all had a token of a false god on their person. The soldiers reasoned that they died due to their homage of a false god. In response, the soldiers and officers took up a collection for a sacrifice to be made in atonement for their sins. The writer of the book commends this action as good and honorable (2 Maccabees 12:39-46).
While some reject this book as not part of the Bible, Jesus seems to reinforce this concept in Matthew's Gospel: "'And whoever speaks a word against the Son of Man will be forgiven; but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come'" (Matthew 12:32). Here, Jesus affirms that sins can be forgiven in this life as well as after death.
Two other key texts undergird the teaching on Purgatory. In the Sermon on the Mount, Jesus states: "Settle with your opponent quickly while on the way to court with him. Otherwise your opponent will hand you over to the judge, and the judge will hand you over to the guard, and you will be thrown into prison. Amen, I say to you, you will not be released until you have paid the last penny." (Matthew 5:25-26).
In the passage, Jesus speaks about a time of judgment, which immediately follows our death. This judgment determines where we will spend eternity. If heaven and hell were the only two possibilities, the concept of being put into prison and paying back what we owe would be meaningless. Instead, this language refers to Purgatory, where we atone and are perfected from our sins.
Lastly, we look to St. Paul, who clearly references a place where our life will be tested by fire. Some of our work will survive and be purified; other parts will be burned up. Even though part will be burned up, Paul says explicitly that the person will be saved by fire (1 Corinthians 3:11-15). What can this be other than the fire of God's love in Purgatory, which purifies our love for Him?
Father Mayo is pastor of Holy Rosary Parish in Warrenton.