“The straight and narrow.” That’s sometimes how we refer to the Christian life. Jesus said it was a “narrow way.” He also said following him meant denying self and picking up a cross.
In 1 Corinthians 5 Paul pointedly takes on the case of a man and woman living together who have no business living together. They both know better. The Church knows better. Everyone is scandalized, but no one wants to do anything. Their pride keeps them from taking action in such a messy relationship. They do nothing.
Some relationships God forbids. Incestuous ones are among them. God simply found them abominable. It was all the reason God needed or gave. If you allow acceptance for these, what will be the excuse for not accepting others? And so Paul commanded the couple be removed from Christian fellowship.
I don’t want to be misunderstood. This relationship was unacceptable. But what really got Paul’s dander up was the fact that the Church knew it and did nothing about it. God calls the family of believers to be closer than that, and to be vigilant against sin. Periodically, we all need to be reminded of the message of 1 Corinthians 5: our relationship with God is a relationship with one another, and it is serious business.