3:6

The tongue is also a fire: This vivid metaphor drives home the point of the preceding sentence. (Jas 3:5; compare Isa 9:18.) The tongue, though a small body member, can be like a fire that spreads quickly and does tremendous damage. James’ strong words in these verses suggest that he may have seen the harm caused by misuse of the gift of speech, whether a bragging claim, a harsh judgment driven by jealousy, or some other divisive remark. (Jas 3:14, 16) When misused in such ways, the tongue can hurt feelings, tarnish reputations, and shatter trust​—sometimes beyond repair.​—See also Pr 16:27; 26:20, 21.

The tongue represents a world of unrighteousness: When uncontrolled, the human tongue represents, or constitutes, a world of every sort of evil and unrighteousness. Misuse of the tongue includes slander, obscenity, false testimony, misrepresentation, reviling, deceptive propaganda, and all forms of erroneous teaching. One reference work thus states: “The tongue, we may say, is the embodiment of all wrong. It utters every wrong emotion and thought and puts every kind of a wrong deed into words.” Some scholars suggest that in this context, the phrase “a world of” can mean “a tremendous amount of.” Certainly, the misuse of the tongue contributes greatly to the evil of this world that is alienated from God.

it defiles all the body: Uncontrolled bad speech defiles not only a man’s tongue but also his whole being. Such misuse of the tongue reveals what a person is inside​—the condition of his figurative heart. Jesus made a similar point when he said: “Whatever comes out of the mouth comes from the heart, and those things defile a man.”​—Mt 15:18, 19.

and sets the whole course of life on fire: “The whole course of life” renders a Greek phrase that literally means “the wheel of the birth (origin).” The idea seems to be that if a person fails to control his tongue, this little organ can cause damage over the entire course of his life, from youth to old age. One reference work suggests that the literal wording used here may have brought to mind the image of a chariot wheel spinning so fast that the axle at its center heats up and ignites. Such a fire would quickly spread to engulf the whole wheel.​—Compare Mr 7:20-23; Ro 3:9-14.

it is set on fire by Gehenna: Decades earlier, Jesus used the fire of Gehenna as a symbol of everlasting destruction. (Mt 5:22 and study note; see also Glossary, “Gehenna.”) Here James stresses a sobering truth: The Christian who misuses his tongue could lose God’s favor and even face the sad end of being erased from existence forever. (Compare Mt 12:31, 32, 37.) In a sense, a person’s misuse of his tongue by his vile speech could bring on him the destructive power of Gehenna. So his hateful words could do more than cause damage to others; they could make him a victim of the fire that he himself started.​—Compare Mt 23:33.