Narrated Abu Dhar: That he heard the Prophet saying, "If somebody accuses another of Fusuq (by calling him 'Fasiq' i.e. a wicked person) or accuses him of Kufr, such an accusation will revert to him (i.e. the accuser) if his companion (the accused) is innocent."
— Sahih Bukhari, Volume 8, Book 73: Good Manners and Form (Al-Adab), Hadith #71
