According to Catholic Apologetics, the doctrine of Purgatory was believed to start in 394 A.D., and was supported by the Catholic Church and upheld by people such as Father Tertullian, Gregory the Great, and St. Augustine. Whether it is believed by other religions of faith or not, Catholics continue to make praying for the dead a priority. The Catechism of The Catholic Church (numbers 1030-1032) actually considers it to be a mortal sin of heresy if it is not practiced.
The Catholic Church describes Purgatory as a place where people go when they die. It is a final purification process that helps them receive the holiness needed to get into Heaven. An example would be if a Catholic dies and they haven’t confessed one of their sins prior to their death, they will go immediately into Purgatory, where they will remain until people left on earth pray for the forgiveness of their sins.
The Purgatory Doctrine contradicts the finality of the forgiveness of sins through Jesus Christ’s death on the cross. In other words, if we have to be purified one last time before God allows us into Heaven, then Jesus dying on the cross wasn’t necessary.
Jesus died once and for all, and because we received forgiveness and salvation when we accepted Him as our Lord and Savior, going to Purgatory to be refined by fire isn’t required. Jesus paid the penalty for our sins and because of that we aren’t required to do anything to earn our salvation or forgiveness.
In Ephesians 2:4-5 (NIV) it states that Because of God’s great love for us, and because he is rich in mercy, He made us alive with Christ, even when we were dead in transgressions-and it is by grace that we have been saved.
Again in Ephesians 2:8-9 (NIV) it states that it is by grace that we have been saved, through faith- and this not from ourselves, it is the gift of God-not by works, so that no one can boast.
Scripture states the will and purpose of God. We should continue to pray for those that are still living around us, both the saved and unsaved, but offering up prayers for those that have already died isn’t biblical, nor does their salvation depend on whether or not we’ve prayed for them. As Christians we should have a desire to reach the lost with the love of Jesus. When they come to know the Lord is based on God’s timing and not our own.
So you see that when we accept Jesus as Our Lord and Savior, we are saved. We do not have to earn our salvation through good works or deeds because He loves us and wants us to have everlasting life.
The Catechism of The Catholic Church