Parashas Shemos
וַיַּ֤עַן מֹשֶׁה֙ וַיֹּ֔אמֶר וְהֵן֙ לֹֽא־יַאֲמִ֣ינוּ לִ֔י וְלֹ֥א יִשְׁמְע֖וּ בְּקֹלִ֑י כִּ֣י יֹֽאמְר֔וּ לֹֽא־נִרְאָ֥ה אֵלֶ֖יךָ יְהֹוָֽה׃
But Moses spoke up and said, “What if they do not believe me and do not listen to me, but say: GOD did not appear toaappear to Or “communicate with.” you?”
Torah Temimah points to Reish Lakish — Shabbos 97a (verified).
לא יאמינו לי — אמר ריש לקיש: החושד בכשרים לוקה בגופו, דכתיב והן לא יאמינו לי, ולקה — דכתיב והנה ידו מצורעת כשלג.
English: “They will not believe me” — Reish Lakish said: One who suspects the worthy is punished in his body, as it is written “But they will not believe me,” and he was punished — as it is written “and behold his hand was leprous as snow.”
Custom
Chazal teach that suspecting the innocent brings bodily punishment, illustrated by Moshe’s hand becoming leprous.