Please read the passage before reading the commentary
Were you ever sent to your room without supper as a child? If so, you were excommunicated. The purpose of the excommunication was to get you to reflect on your behavior so that you could rejoin the family with greater maturity. The excommunication only worked with you because you wanted to be in the family because you needed the family.
In the animal kingdom, at times a herd or group has expelled a member. Outside the group there is danger; it is dangerous for the lone animal because the one alone lacks all the resources needed for survival. The herd protects the vulnerable and cannot protect the animal who lives apart from the herd.
So it was with the Church in Corinth. The congregation protected those within it. It shared its wealth and resources with its members. Even its spiritual growth was shared with the group. If a member were excommunicated, such a one would be cut off from the protection and life of the community.
Paul wanted the man who was living with his father’s wife excommunicated from the community, not to punish and deprive the man of salvation, but to lead him to repentance. As with the child sent to bed without supper, excommunication only works where there is faith in the community, when living in community is necessary for survival, physical or spiritual. Paul wanted the man removed for the destruction of his flesh, that is to say, so that he could grow in spirit and so find salvation of the day of the Lord.
By allowing such a person to continue immoral behavior, the Corinthians were allowing a yeast to grow in their community. Yeast, while it does make bread tastier and easier to work with, also symbolizes evil. A little leaven infiltrates the whole dough the way sin can infect a person’s or community’s own life. Just as the ancient custom was to get rid of the old dough and yeast in spring cleaning, so the community at Corinth had to do spring cleaning with its members.
Sometimes our unit also needs cleaning in the fall, summer and winter. Whenever it takes whatever to clean out the old yeast in our lives we ought to do it. We need to lead lives of sincerity and truth.