The Christian who is caught up in sin is going to be eternally lost if he doesn't repent. Jesus says, "I tell you, no; but unless you repent you will all likewise perish" (Luke 13:3). The reason for church discipline is to try to keep one from being eternally lost.
How does the Bible say the church is to deal with those who are caught up in sin and will not repent? Anything that is less than, more than, or different from what the Bible says is false. We need to speak where the Bible speaks and be silent where the Bible is silent. We need to do things in Bible ways and call things by Bible names. Jesus says in Matthew 18:15-17, "Moreover if your brother sins against you, go and tell him his fault between you and him alone. If he hears you, you have gained your brother. But if he will not hear, take with you one or two more, that ‘by the mouth of two or three witnesses every word may be established.’ And if he refuses to hear them, tell it to the church. But if he refuses even to hear the church, let him be to you like a heathen and a tax collector."
We have an example in First Corinthians of a man, who was a member in the church at Corinth, who was committing fornication with his father's wife. Notice the corrective measure which is commanded by God's word. 1 Corinthians 5:1-13 (KJV), "1It is reported commonly that there is fornication among you, and such fornication as is not so much as named among the Gentiles, that one should have his father's wife. 2And ye are puffed up, and have not rather mourned, that he that hath done this deed might be taken away from among you. 3For I verily, as absent in body, but present in spirit, have judged already, as though I were present, concerning him that hath so done this deed, 4In the name of our Lord Jesus Christ, when ye are gathered together, and my spirit, with the power of our Lord Jesus Christ, 5To deliver such an one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus. 6Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump? 7Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us: 8Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth. 9I wrote unto you in an epistle not to company with fornicators: 10Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then must ye needs go out of the world. 11But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolator, or a railer, or a drunkard, or an extortioner; with such an one no not to eat. 12For what have I to do to judge them also that are without? do not ye judge them that are within? 13But them that are without God judgeth. Therefore put away from among yourselves that wicked person.
The disfellowshipping of this member did cause him to repent, because we read in 2 Corinthians 2:6-8, which was written sometime later, "This punishment which was inflicted by the majority is sufficient for such a man, 7 so that, on the contrary, you ought rather to forgive and comfort him, lest perhaps such a one be swallowed up with too much sorrow. 8 Therefore I urge you to reaffirm your love to him." Church discipline must never be done for vengence, but must be done in love to try to win the erring Christian back to repentance.
The Bible says in Galatians 6:1, "Brethren, if a man is overtaken in any trespass, you who are spiritual restore such a one in a spirit of gentleness, considering yourself lest you also be tempted." We must first go to the individual in love and talk with him personally and urge him to repent. The Bible also says in Jude 22-23, "And on some have compassion, making a distinction; but others save with fear, pulling them out of the fire, hating even the garment defiled by the flesh."
If a person will not repent, the withdrawl of fellowship is commanded in the Bible. 2 Thessalonians 3:6 says, "But we command you, brethern, in the name of our Lord Jesus Christ, that you withdraw from every brother who walks disorderly and not according to the tradition which he received from us." A congregation cannot be pleasing to God and ignore any of His commandments.
Church discipline is not an easy or pleasant thing to do. But sin that is not corrected by repentance will bring reproach on the Lord's church, other members will become lax and also go into sin, and the individual caught up in sin will be eternally lost. The reason the Bible commands church discipline is to try to restore the erring member, so he can go to Heaven, and to keep the church pure. Church discipline must be done in the spirit of love.