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

 1 Corinthians 5:1-13

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. 

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. 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.

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.

God will judge those outside. “Expel the wicked person from among you.”

Why?

Paul heard that there was sexual immorality in the Corinthian church. Paul warns them that they have to get rid of these people from the church. 

Sexually immoral or greedy, an idolater or slanderer, a drunkard or swindler, are not allowed to come to church as brothers and sisters.

Holy Spirit and the Lord are Holy, so keep away from the sins.

How?

Don't allow any sins among us and in my mind. May the Lord give me strength and warning to keep away from sexual immorality.