John Gill Commentary 1 Corinthians 6:8

"Nay, but ye yourselves do wrong, and defraud, and that [your] brethren." — 1 Corinthians 6:8 (ASV)

Nay, you do wrong and defraud
So far were they from taking and acting up to the advice given, that instead of taking wrong, they did wrong; and instead of suffering themselves to be defrauded, they defrauded others:

and that your brethren ;
that were of the same faith, of the same religion, and in the same church and family: in short, neither party, not the plaintiff, nor the defendant, sought anything more or less than to wrong, trick, and defraud each other; such a sad corruption and degeneracy prevailed among them: hence the apostle thought to deal plainly and closely with them, as in the following verses.