1 Corinthians 5:6-13. "A little leaven leavens the whole lump." We are called to share Christ with the world, so we are going to be around sin and sinners. But when that sin is committed by someone who calls themselves a Christian, and they are unrepentant of that sin, Paul says not to associate with them. Leaven leavens the whole lump just like association with a believer who is unrepentant of sin will corrupt others, or appear to do so. The church at Corinth was proud of their acceptance of sinners. Paul tells them not to boast because it's not good. I think they were boastful in their acceptance of sin, instead of sinners. We are called to share God's grace with sinners so they might turn from their sin to God. Corinth understood God's grace incorrectly. Just because we are saved by grace, doesn't mean sin is okay. They were accepting of people's sin, and this was not at all what grace meant. We are still called to judge the actions of believers. There is still a responsibility to live holy lives as believers. Sin is still wrong.
Life seems to get harder and harder. Sin seems to be more and more tempting. I think the early church had the same problems, only they didn't have the whole Bible to study and be encouraged by. We all need fellow believers to come along side us and encourage us too. But, if those believers are living in sin, how can they be encouraging to us? We need to be blameless for the sake of our brothers, just as we need to find ourselves surrounded by believers who are blameless and who can guide us and help us.