1 Corinthians 5:9

I wrote unto you in my epistle to have no company with fornicators; not at all meaning with the fornicators of this world, or with covetous and extortioners, or with idolaters; for then must ye needs go out of the world.

In my epistle ... This most probably refers to another epistle Paul had written to the Corinthians, but which was lost; and, since they misunderstood it, perhaps it was lost providentially. Skilled efforts to make this a reference to previous passages in this same epistle are unconvincing.

The crux of Paul's teaching here is that when he had commanded the Corinthians not to keep company with fornicators (in that lost letter), the congregation had taken it to mean that they were not to associate with ANYBODY guilty of that sin, whether in the church or out of the church. Paul here stated that he did not mean that "at all"; and, if he had meant that, they could have obeyed him only by leaving the present world! What a commentary this is upon the depraved condition of Corinth and the whole world of that era.

Fornicators ... covetous ... extortioners ... idolaters ... Significantly, Paul here extended the prohibition to include association with any grossly wicked people, specifically the four classes mentioned, who might be called "brethren."

Furthermore, despite the fact of its being allowable for Christians to associate with the wicked in the necessary business and commerce of the world, such persons having no connection with Christianity, this is definitely not meant to encourage such associations. Every time a child of God is in the company of the wicked, even in cases where it is necessary and allowable, he runs a certain risk; and there is no way that he should be satisfied and comfortable in such associations. Wall, as quoted by Macknight, said:

It is an everlasting rule that a conscientious Christian should choose, as far as he can, the company, intercourse, and familiarity of good men, and such as fear God; and avoid, as far as his necessary affairs will permit, the conversation and fellowship of such as Paul here describes.[19]