1 Cor 5:5 You are to deliver this man to Satan for the destruction of the flesh, so that his spirit may be saved in the day of the Lord.*

Unlike in Israel, someone who was cut off from the people of God were allowed to enter anew. This is due to the fact that the mark of God’s people is not in the circumcision of the flesh, but of the heart. The sign of a believer is not having sin rule in the body. This is why Paul is adamant about having no leaven (or sin) among the people of God.
        There is a deep sickness that overtakes people when sin is present. Just like yeast causes the whole loaf of bread to rise, not just a section of the bread, so sin spreads like a virus that infects and affects every part of the whole.
        Therefore, we are to purge those in the community who are openly rebelling against God. It is our joy to cast out the brother who is caught in sin and hard-heartedness; because, ultimately, we want him to be restored to God. The ἵνα is so important for us to grasp. We deliver the sinner over to Satan so that his flesh (σαρκός) will be destroyed.
        Who would have thought that Satan is an agent of sanctification. Isn’t this the case in so many situations? Satan has in mind to sift us like wheat (Peter) or, better, to afflict us with boils, take away our riches and family, and cause deep pain (Job). In the end we come out as purified gold (Job 23:10). And although we fall seven times, we will be stood up (Prov. 24:16; Romans 14:4). This is the reason we deliver our sinning brother to Satan…so that he will be refined. Or in order to show that he was not of us (1 Jn. 2:19). In either case, the people of God cannot have sin present among them.
        It is important to note one more point in this chapter. We are not responsible for judging those outside the family. Our judging remains inside the walls of the family. This is something that Christians fail at time and again. We look at the world, Hollywood, the repulsively rich, and say, “How horrible! They shouldn’t do that. They shouldn’t have that.” We are told explicitly that WE shouldn’t do that and WE shouldn’t have that among us. How we fail, Christian! Let us be concerned with the household of God and not try to sanctify the world. Let judgment begin with us and the Lord will exercise his perfect justice on the unbeliever. May we be salt and light to the the world so that the darkness will continue to flee away.