During the first four chapter of I Corinthians, Saint Paul has addressed the problem of factions among the Corinthians. Along the way he has demonstrated his remarkable ability to discern deeper dimensions to present crises, casting on them a far deeper meaning than anyone might have supposed. With their factions the Corinthians are splitting the Body of Christ and alienating themselves from their only hope of salvation. He urges them to consider the treasure they have received and not to be distracted by petty rivalries and bruised egos.
With the fifth chapter he turns to another huge problem. He has been informed that a Christian has "married" his father's wife, his own step-mother. This might raise eyebrows in any culture but to the Jew of that day, it is nothing less than revolting, as in sickening!
As open-minded as we might try to be, there are some alien practices, utterly foreign to our culture, that we find so abhorrent our stomachs rebel.
The Apostle is upset by this man's behavior but his immediate concern is not a couple's sexual relationship. He is worried about the community, the Church:
"Do you not know that a little yeast leavens all the dough? Clear out the old yeast, so that you may become a fresh batch of dough, inasmuch as you are unleavened."
"One bad apple spoils the barrel!" I would suppose most of my readers have thrown out a cluster of rotten apples or tomatoes, and perhaps a clump of moldy bread. Paul didn't have to know about germs or fungi to know that spoil spreads not only in bread but also in the Church.
We can only imagine what excuse the leaders gave for letting this situation go on. Perhaps the fellow was a wealthy donor or a war hero. Perhaps half the Church owed him money. In any case, Paul pronounced judgment and excommunicated him from the Church.
It had to be done for the sake of the Church and every member in it; nor would ignoring the fellow's sin do any favor to him. He had to be excommunicated with the hope that he would realize how disgusting his behavior was; he might yet repent and return.
Just as surgeons sometimes remove diseased parts of the human body, so do Church leaders sometimes expel certain members. It's never easy, pleasant or nice; it may well be messy, upsetting and painful. But it is necessary.