Abu Dharr (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: "If a person calls another person a fasiq (evildoer) or a kafir (disbeliever), and if the one who is being called is not such, then that (statement) returns upon the one who said it." Narrated by al-Bukhari.
Hadith Referenceمشكوة المصابيح / كتاب الآداب / 4816
Hadith Gradingالألبانی:صَحِيحٌ | زبیر علی زئی:صحيح
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «رواه البخاري (6045)»