James 3:5

James 3:5 says, Even so the tongue is a little member, and boasteth great things. Behold, how great a matter a little fire kindleth!  After referring to the bit in the horse's mouth and the rudder of a ship controlling them, James then equated them to the tongue of a person.  It is small compared to other parts of the body, but it can boast of great things, and when it does, it can also control how others see us and often even how we react to others.  James then says that like a little kindling being able to start a large fire, the things that we say can start a fire of iniquity in our relationship with other people.   

Verse six continues, 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.  James expanded on the power of the tongue, or what we say, as a powerful instrument of iniquity.  He said that what we say can defile the whole body, I believe because what we say reflects what we believe.  The tongue can start fires of sin between other people and us. 

Verse seven continues. For every kind of beasts, and of birds, and of serpents, and of things in the sea, is tamed, and hath been tamed of mankind:  James said that all the beasts, birds, servants and things of the sea could be tamed by mankind.  We might say that not all can, but people will always have power over them, even if they are not controlled. 

Verse eight concludes, But the tongue can no man tame; it is an unruly evil, full of deadly poison.   James then stated that unlike all the things mentioned in the previous verse that the tongue cannot be tamed.  The tongue is going to speak what we believe, even if we often attempt to control our words.  We will not be able to prevent what we believe from being expressed by what we say, so if we don't want our tongue to speak evil, then we need to have our mind set on truth of God.  If we do, then we need not worry about what we may say.