Do not put your hand with the wicked to be an unrighteous witness. (ibid. 23:1) Never say anything bad about another Jew, G‑d forbid, because then you will be called to serve as an “unrighteous witness.” When the evil inclination accuses someone, he will call you to bear witness to his words.²). If you must speak disparagingly about some bad trait or person, state clearly that you are not referring to any specific individual, but only to the bad characteristic itself. Rishpei Aish, Mishpotim 44

footnotes: ² R. Moshe of Peshavorsk explained that when the evil inclination rises above to indict a Jew, his words are not heeded, since he is only one voice, and the Torah says: “According to two witnesses . . . shall the matter be established” (Deuteronomy 19:15). Thus, he waits until another individual also speaks badly about the person. Then, he joins with him, to bear witness and accuse (Hakdamos Likutey Torah v’Shas