In Parasha Beha'aloscha both Miriam & Aaron spoke out against Moses. Why was only Miriam afflicted Leprosy and not Aaron as well?
AskTheRabbi.org answered:
Rashi explains that only Miriam was afflicted with Leprosy because she was the one who instigated the criticism of Moses - even though her intentions were entirely pure and she only did it because of her great concern and love for Moshe.