ייִדישער מחשבֿה אויף קהלת 7:21

(4) He should do good to others, speak well of them, judge them favorably, not speak of their faults, forgive them when they speak badly of him, even if they do not deserve this, as written "Even in your thoughts, do not curse a king" (Koheles 10:20), and "You let loose your mouth for evil, and you accustomed your tongue to deceit, you slandered your own mother's son"(Tehilim 50:19). Regarding forgiving others who speak ill of him, the verse says: "and Miriam and Aharon spoke of Moshe", and then "the man Moshe was exceedingly humble", i.e. he had forgiven them. Likewise, the wise man said: "Also take no heed on all words that are spoken" (Koheles 7:21), and adds "For your heart knows that many times you too cursed others"(Koheles 7:22).