Here is the link to Article XII: https://bookofconcord.org/augsburg-confession/of-repentance/
In the first few centuries of the church, one of the questions that Christians wrestled with was the problem of post-baptismal sin. Since baptism is a one-time, unrepeatable event, what happens if you commit mortal sins after being baptized? Can you be forgiven?
In the New Testament, we find that people were normally baptized as soon as they heard and believed the good news about Christ. However, in later centuries, new believers began to delay baptism. Tertullian (c. 155 – c. 220 AD) suggested that, because young people are filled with passion and often give way to temptation, it might be better to wait and get baptized later in life when the passions of the flesh have been tempered.
In the centuries that followed, many people delayed baptism. It is said that the emperor Constantine spent most of his life as a catechumen. He waited to get baptized until he was on his death-bed, because he wanted to avoid the risk of polluting his soul by post-baptismal sin. This was a far cry from what Ananias had said to Paul: “And now what are you waiting for? Get up, be baptized and wash your sins away, calling on his name” (Acts 22:16 NIV).
This issue is closely related to the question of church discipline. In 1 Corinthians 5, Paul instructs the church to excommunicate a brother who had fallen into sexual immorality. Although this is not stated, we can assume that he had been baptized at an earlier time.
Excommunication clearly had the intended effect of leading him to repentance, because in 2 Corinthians 2, Paul urges them to extend forgiveness and welcome him back. Note that there is no command to rebaptize the repentant sinner. He simply needs to be welcomed back into the fellowship and forgiven by the congregation.
When baptized believers fall into sin, they need to repent and believe the gospel. They will then be forgiven. In fact, the Christian life should be marked by daily repentance.
This article states that repentance involves 2 parts: contrition and faith. This directly contradicts Roman teaching; in the Roman Catholic Church, penitent sinners were expected to perform an act of contrition (often a token gesture such as praying a certain number of prayers) prior to receiving the absolution. The Lutheran church did away with this. You are forgiven whenever you repent. However, note that “good works are bound to follow.” A forgiven sinner will voluntarily seek to do good works that please God and neighbor.
This article condemns the idea that Christians can never fall away from the faith. To the contrary, through persistent unrepentance, it is possible to lose the Holy Ghost.
It is true that no one can snatch the elect from God’s hand (John 10:28). God doesn’t abandon you every time you do wrong. In fact, we don’t even know the full extent of our sinfulness: the Psalmist asks God to forgive even those hidden faults that he is not aware of (Psalm 19:12-14)! God is generous and ready to forgive even repeat offenders (see Ezekiel 18:23; Matthew 18:21-22).
However, through persistent rebellion and unrepentance, Christians can walk away from faith (see Hebrews 3:12; 1 Corinthians 10:12; 1 Timothy 1:19).
This article condemns the errors of Novatian. Novatian was a schismatic priest who taught that if a Christian denied the faith, they could never be readmitted into full communion with the church.
This article also condemns the idea that we need to do works to earn forgiveness. Christ’s sacrifice was sufficient.