Lashon haRa occurs when someone tells something negative about somebody else, even if the information is true.
We have explained that Lashon haRa is one of the most serious prohibitions and its effects could be devastating. However, there are some circumstances in which telling Lashon haRa is permitted, and even, mandatory.
The principle is that you could say Lashon haRa about A in order to save B from harm.
In the realm of business, for example, if B asks you about A's integrity, since B is about to engage in business with A, and you know beyond doubt, either by personal experience or by direct knowledge (not rumors!) that A conducts his business inappropriately, then you should tell B the truth about A, in order to protect B. Some rabbis would say that even if B does not ask you for a reference about A, if you found out B is about to engage in business with A, you must warn B.
When you tell B the negative information about A, you must make sure that.
1. You don't exaggerate the facts or overstate A's misconduct.
2. You really have a pure intention in mind: to prevent B from harm, and that you are not saying this out of feelings of revenge or resentment towards A.
The reader should consider this license with utmost seriousness, keeping in mind that our Sages compare Lashon haRa with matters of 'life and death', in the sense that Lashon haRa is often the cause of 'character killing'.
Rabbi Yosef Bitton. YMJC | 130 Steamboat Rd. | Great Neck | NY | 11024