2 Thessalonians 3:6, 14-15

Now we command you, believers, in the name of our Lord Jesus Christ and by His authority, that you withdraw and keep away from every brother or sister who leads an undisciplined life and does not live in accordance with the tradition and teaching that you have received from us.

Now if anyone [in the church] does not obey what we say in this letter, take special note of that person and do not associate with him, so that he will be ashamed and repent. Do not regard him as an enemy, but keep admonishing him as a [believing] brother.