How should a Christian respond to another believer living in open sin without repentance? Aren't we suppose to forgive them and not judge them?
When considering how to respond to a fellow Christian living in open rebellion to the commandments of Christ, we do not have liberty to chose our response. Scripture gives us only one response in 1Corinthians 5:
1Cor. 5:9 I wrote you in my letter not to associate with immoral people;
1Cor. 5:10 I did not at all mean with the immoral people of this world, or with the covetous and swindlers, or with idolaters, for then you would have to go out of the world.
1Cor. 5:11 But actually, I wrote to you not to associate with any so-called brother if he is an immoral person, or covetous, or an idolater, or a reviler, or a drunkard, or a swindler — not even to eat with such a one.
Paul says that the church is not to associate with anyone calling themselves a Christian yet engaging in immoral conduct without repentance. We are to separate ourselves from such a person, not even eating with them. The purpose of the separation is to send a message to the rest of the body that such shameful conduct is not pleasing to the Lord nor conducive to fellowship in the body.
Secondly, isolating the unrepentant sinning believer from the rest of the body protects the church from the harmful effects of their sin.
For more information on this topic, please listen to Lesson 5B of our 1Corinthians study.