Halakhah do Liczb 12:3

And now I shall begin, with the help of the Blessed L–rd to explain how many positive commandments one transgresses in speaking lashon hara and rechiluth, as we projected above.
One who bears tales against his friend, aside from transgressing the negative commandments we mentioned above, also transgresses several positive commandments, which I shall explain, with the help of the Blessed One, one by one.
(1) He transgresses thereby (Devarim 24:9): "Remember what the L–rd your G–d did to Miriam on the way when you went out of Egypt." The Torah exhorted us hereby that we mention verbally, always, the great punishment [leprosy] that the Blessed L–rd brought upon the tzadeketh, Miriam the prophetess — who spoke only about her brother, whom she loved as her soul, whom she raised on her knees, and for whom she endangered her life, to rescue him from the Nile. And she did not speak in denigration of him, but only compared him to other prophets. And she did not speak so to his face to shame him, and not in public, but only to her brother Aaron, privately. And he [Moses] was not offended by all this, viz. (Bamidbar 12:3): "And the man Moses was extremely humble, more than any man on the face of the earth" — in spite of which all her good deeds did not avail her and she was punished with leprosy for this. How much more so will other people, the fools, who are prolix in speaking "great and awesome things" against their friends, be severely punished for this.