Reject and Suspect
Question: I try my best to observe the laws of lashon hara by not only guarding my tongue against gossip and slander but also guarding my ears against accepting what people tell me about other people. How am I to react to a report that someone gives me about a fellow who intends to do me harm?
Answer: There is a fast day in the Jewish calendar related to your question called "Fast of Gedalia". On the third day of the Month of Tishrei Jews fast because on that day about two and a half millennia ago Gedalia ben Achikam, the leader of the Jewish community in Eretz Israel following the destruction of the Beit Hamikdash, and the exile of most of Jewry to Babylon, was assassinated, a tragedy which sealed the doom of hopes for reviving the Jewish presence in their Land.
Gedalia was warned by one of his officers that another officer named Yishmael had been hired by a foreign power to assassinate him, but refused to believe him. This naiveté led not only to his death but also to that of a large group of Jewish pilgrims whom Yishmael murdered after carrying out the assassination for which he gained infamy. The Talmud (Mesechta Nidda 61a) quotes a passage referring to Gedalia as the murderer of these pilgrims, placing blame on him for ignoring the warning given to him regarding Yishmael’s murderous intentions.
The lesson to be learned from this, says the Sage Rava, is that even though it is improper to give total credence to the bad report we hear about someone else, we have a responsibility to treat it seriously and take the necessary precautions.