Explaining a misunderstood term: V. 9. I wrote unto you in an epistle not to company with fornicators; v. 10. yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then must ye needs go out of the world.
Paul had some time before written the Corinthians a letter which is lost, probably having been destroyed immediately for some reason. In that epistle he had used a term which had been understood falsely: Not to become intimate with fornicators.
The Corinthian Christians had interpreted the word in a most rigid sense, namely, that they were bidden under no circumstances, not even in business and in the performance of their duties as citizens, to have intercourse with any persons that were addicted to immoral habits.
The word which Paul had used literally means "to mix oneself up with," and he now interprets it for them: I did not altogether forbid your holding intercourse with the fornicators of this world or with the avaricious, robbers, or idolaters.
If they had the intention of shutting themselves entirely away from all men that were guilty of these sins, even in the course of their ordinary business life, then the inevitable result would be that they must get out of the world. It was impossible to pursue any avocation at Corinth, without coming into daily contact with immoral, rapacious, idolatrous people. Paul was very well aware of this inevitable intercourse; he was far from suggesting or approving the life of anchorites, hermits, and monks.