1 Corinthians 5:2, 6

And you are proud and arrogant! You should have mourned in shame so that the man who has done this [disgraceful] thing would be removed from your fellowship!

Your boasting [over the supposed spirituality of your church] is not good [indeed, it is vulgar and inappropriate]. Do you not know that [just] a little leaven ferments the whole batch [of dough, just as a little sin corrupts a person or an entire church]?