James 3:3-6

3When we put bits into the mouths of horses to make them obey us, we can turn the whole animal. 4Or take ships as an example. Although they are so large and are driven by strong winds, they are steered by a very small rudder wherever the pilot wants to go. 5Likewise the tongue is a small part of the body, but it makes great boasts. Consider what a great forest is set on fire by a small spark. 6The tongue also is a fire, a world of evil among the parts of the body. It corrupts the whole person, sets the whole course of his life on fire, and is itself set on fire by hell.

The tongue, as the rudder, is the means by which we direct our lives into safe harbor or into a hurricane. A ship may be steered by the rudder, but the pilot is the one who directs the rudder. In the same way, the tongue may steer the person's relationships, but what is in a person's heart is what directs the tongue. Just as the rudder can only be controlled by a pilot, the tongue can only be controlled by the heart. Trying to control the tongue any other way is futile. Just like the speakers on a sound system can only play the music that is on the disk in the CD player, a person's tongue can only communicate what is in his heart. When we harbor bitterness, fear, resentment or anger, regardless of how well we think we are able to filter it before it reaches the tongue, it comes out and is heard, and our relationships get steered into places we don't want to go. In contrast, people who are full of the Holy Spirit are skilled with the tongue, always offering encouragement and saying the right things at the right time.