2 Thessalonians 3:6; 2 Thessalonians 3:14

6 Brothers and sisters, in the name of our Lord Jesus Christ we order you not to associate with any believer who doesn't live a disciplined life and doesn't follow the tradition you received from us.
14 It may be that some people will not listen to what we say in this letter. Take note of them and don't associate with them so that they will feel ashamed.