16 Jesus said, “Even after all this, are you still so foolish? 17 Don’t you understand that whatever goes into the mouth enters the stomach and then passes out into the sewer? 18 But the things that come out of the mouth come from the heart, and these things defile a person. 19 For out of the heart come evil ideas, murder, adultery, sexual immorality, theft, false testimony, slander.
Matthew 15:10-20 (NET)
4 Look at ships too: Though they are so large and driven by harsh winds, they are steered by a tiny rudder wherever the pilot’s inclination directs. 5 So, too, the tongue is a small part of the body, yet it has great pretensions. Think how small a flame sets a huge forest ablaze. 6 And the tongue is a fire! The tongue represents the world of wrongdoing among the parts of our bodies. It pollutes the entire body and sets fire to the course of human existence—and is set on fire by hell.
James 3:1-12 (NET)