The General Epistle of James, written by the brother of our Lord, provides ethical instruction for all Jewish people who have become Christians. It is clear and practical in its dealing with Christian behavior.

James 3

3:6 And the tongue is a fire, a world of iniquity: so is the tongue among our members, that it defileth the whole body, and setteth on fire the course of nature; and it is set on fire of hell.