Hadith on Takfir: He commits unbelief by wrongly accusing believers

Abu Sa’id reported: The Messenger of Allah, peace and blessings be upon him, said, “A man never accused another man of unbelief but that it backfires on one of them. Either he is an unbeliever, or he has committed unbelief by his accusation of unbelief.

Grade: Sahih li ghayrihi (authentic due to external evidence) according to Al-Albani

عَنْ أَبِي سَعِيدٍ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى الِلَّهِ عَلَيْهِ وَسَلَّمَ مَا أَكْفَرَ رَجُلٌ رَجُلا قَطُّ إِلا بَاءَ أَحَدُهُمَا بِهَا إِنْ كَانَ كَافِرًا وَإِلا كَفَرَ بِتَكْفِيرِهِ

251 صحيح ابن حبان

2775 المحدث الألباني خلاصة حكم المحدث صحيح لغيره في صحيح الترغيب