Riyad as-Salihin, Book 18, Hadith 1733 (In-Book) ⓘ
Abu Dharr (May Allah be pleased with him) said: I heard the Messenger of Allah saying, "If somebody accuses another of disbelief or calls him the enemy of Allah, such an accusation will revert to him (the accuser) if the accused is innocent."[Al-Bukhari and Muslim].
وعن أبي ذر رضي الله عنه أنه سمع رسول الله صلى الله عليه وسلم يقول: "من دعا رجلا بالكفر، أو قال: عدو الله، وليس كذلك إلا حار عليه" ((متفق عليه)). حار رجع.