Consider some Biblical principles:
The Bible teaches that no one can be saved who does not believe in God (Hebrews 11:6) and repent of their sins (Luke 13:3), along with baptism into Christ for the remission of sins and new spiritual birth (Acts 2:38, John 3, Romans 6). There is no other way; no one comes to the Father except through the blood of Jesus Christ (John 14:6, 2 Corinthians 5:21).
This means that regardless of how much or how little someone sins, if they are not washed in the blood of Christ, they are lost (Romans 3:23, Romans 6:23).
Therefore, teaching a lost person how to sin less does not save them.
On the other hand, for those who are saved, continuing to live in sin endangers or even condemns us. We must walk in the light if we wish to be continually cleansed (John 3:19-21, 1 John 1:6-7). If we are born of God, we do not go on sinning (1 John 3:9). If we continue to willfully engage in sin, we are condemned; Christ’s blood no longer covers us (Hebrews 10:26).
Therefore, exhorting a saved person to come to the light and seek true, ongoing repentance is vital to their salvation.
Do you think Paul might have had these principles in mind when he wrote 1 Corinthians 5:9-13? In that passage, he says “For what have I to do with judging outsiders? Do you not judge those who are within the church? But those who are outside, God judges.”
Those who reject Christ or who do not obey his words (John 14:15) are already lost. God has already handed down that judgment. You cannot get more lost than just plain lost. On the other hand, those who have obeyed the gospel but are finding themselves ultimately unwilling to finish what they have started are the ones who can benefit from exhortation and discipline. God’s own children are the one’s whom He disciplines (Hebrews 12:6-8).
The message conveyed by these principles is not that we should avoid speaking out about the sins of the world. Rather, it is a reminder that no amount of speaking out against sin will be effective if it is not accompanied by the message of the gospel. Until a heart is changed by the gospel of Jesus Christ, changing an individual’s actions will not address the core heart problem, nor will it save them.
These thoughts also serve as a reminder of the serious nature of habitual sin among believers. For the child of God, submission to God’s will as it pertains to particular matters or behavior and attitude is crucial. Refusal to submit will cause us to forfeit that which Christ died to give us and we came so close to attaining.