Musar zu Schemot 4:2

ויאמר ה' אליו מה זה בידך. G–d said: "what is this in your hand?" (Exodus 4,2). Moses was punished with צרעת for having said that Israel would not believe him, even though his motives in saying so had been pure, i.e. he had wondered how he could overcome that lack of belief. This teaches how careful one has to be not to impugn the honour of Israel.

(Shemoth 4:2): "What is this in your hand? And he said: 'A staff.'" (see Rashi, to the effect that He said to Moses: "Mizeh ["From this"] that is in your hand, you deserve to be smitten" [for having wrongly suspected the innocent]. From this we can understand that in all instances of lashon hara — it being known from Tosefta Peah that punishment is exacted for them in this world, with the principal remaining [for punishment] in the world to come — there is no necessity of adducing a distant cause for his punishment, but [it can readily be understood] as proceeding from what is immediately "at hand."