In Matthew 18, Jesus teaches about how to deal with a brother who has sinned against us. The end of the process, if it fails to restore, is: "And if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector." [ESV]
I am wondering if this is a new idea? Or if it was part of the Old Covenant as well. Where people expelled from the community of believers in the Old Testament?