1 Corinthians 5:9

9.I wrote to you in an epistle. The epistle of which he speaks is not at this day extant. Nor is there any doubt that many others are lost. It is enough, however, that those have been preserved to us which the Lord foresaw would suffice. But this passage, in consequence of its obscurity, has been twisted to a variety of interpretations, which I do not think it necessary for me to take up time in setting aside, but will simply bring forward what appears to me to be its true meaning. He reminds the Corinthians of what he had already enjoined upon them — that they should refrain from intercourse with the wicked. For the word rendered to keep company with, means to be on terms of familiarity with any one, and to be in habits of close intimacy with him. (294) Now, his reminding them of this tends to expose their remissness, inasmuch as they had been admonished, and yet had remained inactive.

He adds an exception, that they may the better understand that this refers particularly to those that belong to the Church, as they did not require to be admonished (295) to avoid the society of the world. In short, then, he prohibits the Corinthians from holding intercourse with those who, while professing to be believers, do, nevertheless, live wickedly and to the dishonor of God. “Let all that wish to be reckoned brethren, either live holily and becomingly, or be excommunicated from the society of the pious, and let all the good refrain from intercourse and familiarity with them. It were superfluous to speak as to the openly wicked, for you ought of your own accord to shun them, without any admonition from me.” This exception, however, increases the criminality of remissness, inasmuch as they cherished in the bosom of the Church an openly wicked person; for it is more disgraceful to neglect those of your own household than to neglect strangers.