Then there is the rapier tongue; that is fairly obvious: pain and bleeding and hostility. You can see it in the context of the farm that Solomon began this whole passage with.
The tongue of the wise is gentle by comparison. It aims at the healing of the other, and knows that this cannot be achieved by violent words or criticism alone. Christ, when he was on earth, had reason to say many harsh things to people, but moderated his words to make them more acceptable, more effective. Those we try to help must sense that we are kindly disposed towards them. The tongue of the righteous must be able to comfort, encourage, protect, nurture, and coax those it tries to help, and not to do so in an overbearing way (Lawson). Lawson also comments that the wise tongue must know when to speak.
Sword-like words are very habit-forming. You spend two or three weeks letting your self-control just switch off, just stabbing out and lashing out at people, and it is remarkably habit-forming. With particular people you begin to speak rather nastily, unpleasantly towards someone, that habit almost fixes itself upon your relationships with that person. The world has no means of off-loading its tensions and emotions except by hitting back and seeking vengeance. The great mark of Christian character should be health-giving, always thinking of the objective, always stewarding words to a good outcome - with children, with people around us.