What is so heinous about gossip and idle chatter that those guilty of it in Biblical times are afflicted by tzara'at?
It is very difficult, and sometimes nearly impossible, to do teshuva (repent) for having spoken negatively about another person. The speaker must genuinely feel sorry, must decide never again to speak in this manner, and must apologize and ask for forgiveness from the person spoken about. Unfortunately, spoken words cannot be taken back so easily once they are heard by others. A person who speaks negatively causes bad feelings and strife and may even change the listener's opinion about the person being discussed.
As parents, it is particularly important to refrain from both speaking and listening to gossip with our children. We must remember that gossip, even if truthful, is demeaning and demoralizing. It attempts to bring down people in order to make ourselves feel better. Each time we speak badly about someone, we feel less inclined to improve ourselves.
Rabbi Stephen Baars, on www.aish.com warns, "A family that engages in gossip creates a real fear that any mistake will be looked at in a disparaging light. Children develop a fear of failure, knowing that their faults will be harshly examined, illuminated and even publicized in a demeaning manner. And, on top of that, they will be discussed behind their backs, with no form of defense or recourse."
The Hebrew expression for gossip and idle chatter is lashon hara, literally "evil tongue." To protect the tongue from misuse, G-d gives us two gates: our teeth and lips. Before we use our tongues, we should shut the gates and carefully consider whether or not we should speak. As the psalmist writes, "Guard your tongue from evil and your lips from speaking deceitfully." (Psalms 34:14)