After discussing with the Corinthians the notion that one who is a Christian cannot be in communion with sin or sinners anymore than righteousness can have fellowship with lawlessness, or light with darkness, or Christ with Satan, or the temple of God with the temple of idols, Paul strongly encourages the Christians there to Come out from among them and be separate, says the Lord. Do not touch what is unclean, and I will receive you (2 Corinthians 6:17). Not only does Paul use the filthiness or the defilement that comes from sin as a motivation, he shows them the promises of God that accompany such a detachment from sin: "As God has said: 'I will dwell in them And walk among them. I will be their God, And they shall be My people'" (2 Corinthians 6:16). And then, "I will be a Father to you, And you shall be My sons and daughters, Says the LORD Almighty" (2 Corinthians 6:18). What wonderful promises and what amazing motivation to separate ourselves from the defilement of sin! In context, the "unbelievers" from which he commands the Corinthians to be separate are the false teachers who had come in among them. He calls false teachers "unbelievers", even though they believed in Jesus. Paul continues the thought of separation in the next chapter saying, "Therefore, having these promises, beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God" (2 Corinthians 7:1).
It is the promises of Satan that got us involved in sin. He held up the lust of the eye, the lust of the flesh, and the pride of life before us to entice us away from the Spirit of God ... to entice us into a walk ordered by the desires of the flesh rather than a life in concert with the Spirit of God. It was those empty promises that led us away from God. The results of those promises are apparent in the world: sickness, pain, suffering, hate, murder, war, rape, lying, envy, greed ... you name it. It all came/comes as the result of sin controlling our hearts. It all came/comes as the result of fleshly desires ruling our lives and conduct. It all comes as the result of believing the lie. So Paul, through the Spirit, gives us the answer: "Do you want God to live with you? Do you want to live with God? Do you want God walking around in your life? Do you want to be God's people, His sons, His daughters? Do you want God as your Father? Then cleanse yourself from all filthiness of the flesh and spirit (cleanse the whole man) and let God work in your life to complete the holiness (purity) that He gave you when you were baptized." You can't have it both ways. You can't have an "uncircumcised heart" that desires sinful things and have God at the same time. Sin can have no communion with God!
Make your choice. Walk in one or the other. Received the promises of the one you choose. But don't come whining to God when your life is filled with the product of sin. Oh, but wait ... that is exactly the invitation of God. When you come to your self, when you understand what God did for you to be cleansed, when you are tired of sin and it's consequences, He invites you to come to Him and be clean. Mind you, it has to be sincere, and it has to be the whole person that is cleansed, but know this, until your dying breath the invitation is open for you.