The Apostle Paul
1 Corinthians 5:11BSB·traditional attribution

But now I am writing you not to associate with anyone who claims to be a brother but is sexually immoral or greedy, an idolater or a verbal abuser, a drunkard or a swindler. With such a man do not even eat.

John Calvin Reformed @genevareformer

11. If he who is called a brother In the Greek there is a participle “Au texte Grec il y a de mot a mot, Si aucun frere nomme,” etc.; — “In the Greek text it literally, If any one, called a brother,” etc. without a verb. It is so according to the common reading, which is as follows: — ἐάν τις, ἀδελφὸς ὀνομαζόμενος, ἣ πόρνος, ἣ πλεονέκτης, κ. τ.

Matthew Henry Presbyterian @wholebiblehenry

Here the apostle advises them to shun the company and converse of scandalous professors. Consider, I. The advice itself: I wrote to you in a letter not to company with fornicators, Co1 5:9. Some think this was an epistle written to them before, which is lost.

Commenting on 1 Corinthians 5:9-13

John Gill Reformed Baptist @doctorgill

But now have I written unto you,.... Which shows, that what he had written before was at another time, and in another epistle; but not that what he was now writing was different from the former, only he explains the persons of whom, and the thing about which he has before written: not to keep company, if any man that is called a brother, be...