https://en.wikipedia.org/wiki/Indulgence#Protestant_Reformation
Fortunately we have Colossians 2:13-14 to counter this false teaching of Roman Catholicism.
13When you were dead in your transgressions and the uncircumcision of your flesh, He made you alive together with Him, having forgiven us all our transgressions, 14having canceled out the certificate of debt consisting of decrees against us, which was hostile to us; and He has taken it out of the way, having nailed it to the cross.
Our sin debt was paid in full at the Cross. The Greek definitions behind this passage indicates our sins are wiped away...erased.
If the blood of Christ is insufficient to remove our sins then nothing mere man can do will.
The false notion of mortal sins causing one to lose salvation is again countered by Ephesians 1:13-14
13In Him, you also, after listening to the message of truth, the gospel of your salvation—having also believed, you were sealed in Him with the Holy Spirit of promise, 14who is given as a pledge of our inheritance, with a view to the redemption of God’s own possession, to the praise of His glory.
We have nothing in the NT to ever indicate a believer can unseal what God has sealed...or that God unseals the believer.
Colossians 1:13-14 He has delivered us from the domain of darkness and transferred us to the kingdom of his beloved Son, in whom we have redemption, the forgiveness of sins.
Born again/born from above believers are already in heaven with Christ in the spiritual realm.
When we die, the body is gone, along with the old sin nature and all that is left is the new man which is without sin and already seated in the heavenly places with Christ Jesus.
Ephesians 2:1-10 And you were dead in the trespasses and sins in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience— among whom we all once lived in the passions of our flesh, carrying out the desires of the body and the mind, and were by nature children of wrath, like the rest of mankind.
But God, being rich in mercy, because of the great love with which he loved us, even when we were dead in our trespasses, made us alive together with Christ—by grace you have been saved— and raised us up with him and seated us with him in the heavenly places in Christ Jesus, so that in the coming ages he might show the immeasurable riches of his grace in kindness toward us in Christ Jesus. For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast. For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them.
Fortunately I don’t rely on wikipedia for church history or my faith.
Matt 6:14 For if you forgive others their trespasses, your heavenly Father will also forgive you; 15 but if you do not forgive others, neither will your Father forgive your trespasses.
Matt 7:21“Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but only the one who does the will of my Father in heaven.”
Ephesians 2:8 For by grace you have been saved through faith, and this is not your own doing; it is the gift of God— 9 not the result of works, so that no one may boast. 10 For we are what he has made us, created in Christ Jesus for good works, which God prepared beforehand to be our way of life.
1 Corinthians 9:27 but I punish my body and enslave it, so that after proclaiming to others I myself should not be disqualified.
James 1:22 But be doers of the word, and not merely hearers who deceive themselves. 23 For if any are hearers of the word and not doers, they are like those who look at themselves in a mirror;
James 2:14 What good is it, my brothers and sisters, if you say you have faith but do not have works? Can faith save you? 15 If a brother or sister is naked and lacks daily food, 16 and one of you says to them, “Go in peace; keep warm and eat your fill,” and yet you do not supply their bodily needs, what is the good of that? 17 So faith by itself, if it has no works, is dead.
James 2:18 But someone will say, “You have faith and I have works.” Show me your faith apart from your works, and I by my works will show you my faith. 19 You believe that God is one; you do well. Even the demons believe—and shudder. 20 Do you want to be shown, you senseless person, that faith apart from works is barren? 21 Was not our ancestor Abraham justified by works when he offered his son Isaac on the altar? 22 You see that faith was active along with his works, and faith was brought to completion by the works. 23 Thus the scripture was fulfilled that says, “Abraham believed God, and it was reckoned to him as righteousness,” and he was called the friend of God.
James 2:24 You see that a person is justified by works and not by faith alone. 25 Likewise, was not Rahab the prostitute also justified by works when she welcomed the messengers and sent them out by another road? 26 For just as the body without the spirit is dead, so faith without works is also dead.