1 Corinthians 5:1-11 NIV
It is actually reported that there is sexual immorality among you, and of a kind that even pagans do not tolerate: A man is sleeping with his father’s wife. And you are proud! Shouldn’t you rather have gone into mourning and have put out of your fellowship the man who has been doing this? For my part, even though I am not physically present, I am with you in spirit. As one who is present with you in this way, I have already passed judgment in the name of our Lord Jesus on the one who has been doing this. So when you are assembled and I am with you in spirit, and the power of our Lord Jesus is present, hand this man over to Satan for the destruction of the flesh, so that his spirit may be saved on the day of the Lord.
Your boasting is not good. Don’t you know that a little yeast leavens the whole batch of dough? Get rid of the old yeast, so that you may be a new unleavened batch—as you really are. For Christ, our Passover lamb, has been sacrificed. Therefore let us keep the Festival, not with the old bread leavened with malice and wickedness, but with the unleavened bread of sincerity and truth.
I wrote to you in my letter not to associate with sexually immoral people— not at all meaning the people of this world who are immoral, or the greedy and swindlers, or idolaters. In that case you would have to leave this world. But now I am writing to you that you must not associate with anyone who claims to be a brother or sister but is sexually immoral or greedy, an idolater or slanderer, a drunkard or swindler. Do not even eat with such people.
NIV: New International Version