Simon Peter, the Rock and the Pope
To understand the Catholic teaching on Purgatory and Indulgences first we have to understand how a person is saved. Protestants believe in the imputed righteousness through Jesus’ finished sacrifice on the cross. The Catholic Church also teaches that Jesus’ sacrifice on the cross provided sufficient Grace for everyone to be saved. The Church teaches that when Jesus said “it is finished” He is referring back to the Passover meal He celebrated with His disciples where He said He would “…not drink of the fruit of the vine until He drank it in His Father's Kingdom.” Most Protestants skip over the John 19:28 passage where Jesus says “I thirst” reminding us of how He would not drink of the fruit of the vine. When Jesus says “It is finished” on the cross He is referring to the New Testament Passover that He stared in the upper room being finished, because He had just drank the wine finishing that Passover meal.
Some Protestants hold the view invented by Martin Luther that through Faith in Jesus we are covered by His righteousness and APPEAR Holy to God. Others hold the view invented by John Calvin that through Grace the elect are hidden in Christ's righteousness and APPEAR Holy to God. Neither of these two new theologies actually have a plan to make a Christian Holy. They expect a Christian to act Holy but they don't have to. The Catholic Church teaches us that we are washed clean of all previous sin and made Holy through baptism. Once we are washed clean of sin and incorporated into the Body of Christ, we maintain that righteousness through the Sacrament of Reconciliation. Our understanding of doing penance and praying for the dead come from the Jewish understanding of sin, reconciliation and praying for the dead.
When a person is baptized all previous sin is washed away as in Acts chapter 2 and 9. All post Baptismal sin requires some form of penance to heal our relationship with God. Starting with the Jewish understanding of forgiving sins, animals were offered to reconcile us with God in Leviticus. In 2Samual after Nathaniel forgave David for his sin with Bathsheba, he told David his son would die. This tells us something has to be done to reconcile us to God even after forgiveness. Christ's death on the cross reconciles all of our past sins with God when we come to Faith. It also provides the Grace for us to be sanctified. We still need to offer something back to God to heal the wound in our relationship with Him caused by our sin. The Catholic Church teaches our sins are not “hidden” in Christ, but easily visible to God.
Purgatory is the stage on the way to Heaven where any penance still due is completed. You can do your penance now or in Purgatory. The Jews also prayed for the sins of their dead in 2 Maccabees chapter 12 and still offer prayers for their dead today. For these prayers to have any effect there must be a place after death where sins can be forgiven. In Matthew 21 Jesus says that blasphemy against the Holy Spirit cannot be forgiven in this life or the next which implies some sins can be forgiven in the next life. In Revelation 21 we learn that nothing unclean can enter Heaven. Jesus provides all the Grace we need to be saved, but we don't always allow that Grace to fill us and sanctify us in this life, so it needs to be finished in us before we enter Heaven. Since few of us reach full sanctification here on Earth, there has to be a way to finish sanctification on the way to Heaven. Some people are still living with Luther's misunderstanding that Jesus' sacrifice covers our sins like snow over a dung heap. If that is their understanding than all those sins still need to be reconciled in Purgatory before entering Heaven.
In 2Corinthians 5:1-8 Paul tells us that when we die we are not necessarily instantly present with the Lord. “For we know that if our earthly house, this tent, is destroyed, we have a building from God, a house not made with hands, eternal in the heavens. For in this we groan, earnestly desiring to be clothed with our habitation which is from heaven, if indeed, having been clothed, we shall not be found naked. For we who are in this tent groan, being burdened, not because we want to be unclothed, but further clothed, that mortality may be swallowed up by life. Now He who has prepared us for this very thing is God, who also has given us the Spirit as a guarantee. So we are always confident, knowing that while we are at home in the body we are absent from the Lord. For we walk by faith, not by sight. We are confident, yes, well pleased rather to be absent from the body and to be present with the Lord” (2 Corinthians 5:1–8).This does not say that we are instantly present with the Lord. It says that we would be “pleased to be absent from the body and present with the Lord”. When we compare this language to 1 Corinthians 15:51–54, also written by Paul, it becomes even clearer. The passage reads: “Behold, I tell you a mystery: We shall not all sleep, but we shall all be changed— in a moment, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, and the dead will be raised incorruptible, and we shall be changed. For this corruptible must put on incorruption, and this mortal must put on immortality. So when this corruptible has put on incorruption, and this mortal has put on immortality, then shall be brought to pass the saying that is written: ‘Death is swallowed up in victory.’ ” From this we learn that at death, or the final resurrection, we shall be changed from corruptible (capable of sinning) to incorruptible (incapable of sinning).
In 2 Timothy chapter 1 we find Paul praying for his dead friend Onesiphorus. Praying for the dead in Hell can’t help them. Praying for the dead in Heaven is unnecessary, so there must be some state of being between life on earth and life in Heaven.
Many Protestants think the Church makes money by selling indulgences or by having Masses said for the dead. Although there was a brief time when a Bishop in Germany was selling indulgences without authorization, the sale of indulgences is not the normal practice of the Church. A person can gain an indulgence for themselves, or for a loved one who has previously died, by offering certain practices as a form of penance for the person receiving the indulgence. The practice of indulgences goes back to at least the 200s in Christianity. Before Christianity became a tolerated religion in 311AD, Christians were being severely persecuted on and off by the Romans. When some people sacrificed to the Roman Emperor to save their life, they were expelled from communion with the Church until they did a penance which could last for years. Some of these penitents appealed to Christians that were in prison, because they refused to sacrifice to the Emperor, to appeal to the local Bishop to have their penance reduced. The thought was that the merit of Grace of the condemned prisoners could be given to the penitents that were still free. The local Bishops were not quick to let these penitents off easy, but the understanding that since we are all members of the Body of Christ, one member is allowed to help another member with their penance. In 115AD Polycarp of Smyrna, who learned the Faith from the Apostle John, wrote a cover letter for the letters of Ignatius of Antioch that he was forwarding to the Church in Philippi. In his letter he quotes from the Book of Tobit that says “alms cover a multitude of sins”. This is where the Church gets its teaching that alms for the poor can be offered as penance for sins. The Church teaches that the excess Grace, merited by other members of the Body of Christ, His Church, can be offered to those who are not yet in Heaven, so that they can be fully sanctified and worthy of entry into Heaven. Just as we can help each other do things on Earth, the Saints in Heaven can help sanctify us here on Earth. All of this only makes sense when you think of us as members of the Body of Christ that can help each other, and that we have to be Holy before we can enter Heaven.