Discipline might be the hardest task a congregation is given by God. We know it’s necessary to preserve the sanctity of the church and to prevent the sinning Christian from being eternally condemned.
There’s two distinct processes in discipline. The first involves a church deciding that they will withdraw themselves from a sinning Christian. There are several roadblocks Satan puts in the way to prevent church discipline (“They’re family,” “There’s been too much time,” “They’ve withdrawn from us,” etc.). However, if a congregation sees its necessity, they will follow Paul’s decrees: “Therefore purge out the old leaven, that you may be a new lump, since you truly are unleavened. For indeed Christ, our Passover, was sacrificed for us” (1 Corinthians 5:7) and, “But we command you, brethren, 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” (2 Thessalonians 3:6).
The second process involves how individual Christians act toward the unrepentant Christian. Again, Paul teaches, “I wrote to you in my epistle not to keep company with sexually immoral people … But now I have written to you not to keep company with anyone named a brother, who is sexually immoral, or covetous, or an idolater, or a reviler, or a drunkard, or an extortioner — not even to eat with such a person” (1 Corinthians 5:9-11) and, “And if anyone does not obey our word in this epistle, note that person and do not keep company with him, that he may be ashamed. Yet do not count him as an enemy, but admonish him as a brother” (2 Thessalonians 3:14-15).
A lot of Christians disregard the second process by saying that the sin is “their business” — meaning the offending Christian. I don’t doubt it’s “their business” since they did it, but it’s the faithful Christian’s business when it involves upholding divine directives. We’d better respect the seriousness of these commands instead of glibly saying, “That’s their business” and then acting toward them like nothing has happened. God judges all unrighteous behavior, which by definition implies not doing what God decidedly says to do.