Wisdom is better than weapons of war: but one sinner destroyeth much good. - Ecclesiastes 9:18
The first thing I think about here is the story of Achan and the battle of Ai. In that account the nation of Israel had just had a great victory at Jericho, but were defeated at the battle of Ai which they should have won easily.
Hw could they lose such an easy battle? Achan, one of the men of Israel has sinned by taking some of the loot for himself.
The picture is pretty clear. One sinner can make a mess of things for everyone else.
We are primarily talk about something dealing with God’s people. Achan sets the example in the Old Testament, and in the New Testament we have an example of the truth in the church at Corinth.
A man in the church there was have sexual relations with his mother-in-law. The church has tried to get him to confess and repent and lay aside his sin. Still he continued, but something had to be done.
So Paul told the church to ‘put him out’ until he repented.
That sounds harsh, but it worked. The man was restored.
It is important that the church deal with sin in her ranks. Tolerating a little sin does a lot of damage. It is never to be done in a haughty, arrogant, or punishing way. The goal is always to restore the erring member.
But one sinner can do a lat of harm, to himself and to the church. Our task is to admonish and help get him on the right path.