Some people would never physically injure another person. The sight or even the thought of violence makes them cringe. They may not realize that their words can cause more damage than their fists ever could. A physical injury eventually heals and may even be forgotten, but an insulting word can penetrate to the depths of someone's being and continue to reverberate, long after a mere physical wound would have healed.
I have seen this phenomenon in my own practice. Many children are spanked by their parents. Still, with the exception of cases of severe abuse, my patients rarely, if ever, mention the spanking as a trauma. Not so with degrading words. After thirty or more years, patients will remember having been called "stupid," "rotten," or "a no-good bum." A child who was not spanked, but was instead disciplined with shame and made to feel that he or she was a disgrace, is likely to retain that feeling for decades and may harbor an attitude of shame that affects everything that he or she does.
While we are taught to refrain from striking out in anger, we are far less restrained when it comes to verbal lashings. Whether we direct them towards spouses, children, or peers, we should be aware of the impact that words can have. The verse cited above correctly describes the tongue as a sharp, penetrating arrow, which can be every bit as lethal as any physical weapon.
Some people have a wise custom. When they become angry, they clamp their lips tightly. The anger will safely dissipate and the words which could have stung for years never come out.