"When I wrote to you before, I told you not to associate with people who indulge in sexual sin. But I wasn't talking about unbelievers who indulge in sexual sin, or are greedy, or cheat people, or worship idols. You would have to leave this world to avoid people like that. I meant that you are not to associate with anyone who claims to be a believer yet indulges in sexual sin, or is greedy, or worships idols, or is abusive, or is a drunkard, or cheats people. Don't even eat with such people."
We have to make sure that the person (Jesus) whom we say we believe is being seen in our lives, and that we are making an effort and working on living that belief out. If there is no change in our behavior after knowing Christ there is no reason to say we are a believer. Paul says, "...I meant that you are not to associate with anyone who claims to be a believer yet indulges..." Indulges means to yield to an inclination or desire. Also to allow oneself to follow one's will. When we indulge in something we are purposely going against what The Spirit is showing us and living for ourselves. Jesus said in Mark chapter 8 verse 35, "If you try to hang on to your life, you will lose it. But if you give up your life for my sake and for the sake of the Good News, you will save it."
If you say you are a Christian or a (believer) it doesn't make you sin free but your heart is changing because God has given us His Spirit to guide, comfort and teach us what is right and holy. When we don't have a relationship, even though we say we believe, it's hard to have transformation. We might have information but that does us no good. When we hang out with other believers it should be a time of challenge and joy and hope because we know we are new in Christ.
If people say one thing and do another we as believers need to help them see the truth. Paul continues on in verses 12-13 by saying, "It isn't my responsibility to judge outsiders, but it is certainly is your responsibility to judge those inside the church who are sinning. God will judge those on the outside; but as the Scripture say, 'You must remove the evil person from among you." This seems harsh but we need our direction and our obedience. That is why we read God's word, pray and co-labor with Him to learn and change. Jesus perfects our faith, the Holy Spirit comforts us by reminding us what is right and wrong and also about the strength we have because of Jesus.
We are not looking for people to stay away from we are looking for people we can love and help guide or disciple so they become fully devoted followers and doers of the word not just hearers of the word. We also will never be perfect and need to continue to ask, seek and knock so our lives show what we believe about our eternal destination. Amen