DEUT1350 We must publicize how reprehensible it is to speak against others. In a public letter, the Chofetz Chayim cites the Ramban who explains that this verse obliges us to tell our children and future generations how reprehensible loshon hora is. We must publicize how wrong it is to speak against others. People must realize that refraining from loshon hora is not merely a meritorious trade, but an obligation of the highest magnitude. Unfortunately, too many otherwise observant Jews behave as if the prohibition against loshon hora did not exist. Even those who are careful do not feel as upset when they happen to speak or hear loshon hora as they would if they accidentally were to eat pork. Therefore, we must do all we can to publicize the gravity of speaking loshon hora. Moreover, if you influence others not to speak loshon hora, you will find that you yourself will be much more careful with what you say. (Michtevai Chofetz Chayim, letter 35). Since this verse comes to teach us to refrain from speaking loshon hora, the question arises why the Torah describes Mariam's sin. Rabbi Simcha Zissel Ziv writes that this teaches us the principle that it is permissible to relate derogatory information about someone when one's sole purpose is to teach another how to behave. It is a great merit for Miriam that others will learn from her experience to be careful not to speak loshon hora. This is the reason the Torah mentions the sins of various individuals and groups. (Chochmah Umussar, vol. 2, . 459, essay 340). The Chofetz Chayim writes that if a person sees faulty traits in someone (for example, conceit, a bad temper, lack of diligence in Torah study), and fears that his children or students might imitate that person, it is proper to warn them about that individual's shortcomings. The prohibition against disparaging others applies only when the words are said with intent to belittle and disgrace the person spoken about. If the intent is to alert others not to follow in the footsteps of someone who has faulty traits, it Is permitted to mention that person's faults, and it is even considered a mitzvah. It is necessary in such cases to clearly explain the purpose of your derogatory words in order to avoid any misunderstanding on the part of your children or students. If an entire community acts improperly and you fear that someone may copy their faults, you are permitted to point out their shortcomings in order to prevent a person from mingling with them. If you have first-hand knowledge of a person's fault (that is, you have witnessed it yourself), you may deliver the warning as an undisputed fact. If you only know the information from hearsay, you must give the warning in the following manner: "I have heard from others that…" Although the speaker is obligated to mention someone's faults to prevent imitation, the listeners are not allowed to except information as the absolute truth. They are only permitted to be wary in order to protect themselves from a harmful influence. (Chofetz Chaim 4:10 and B'air Mayim Chayim 42; Guard Your Tongue, p. 63).