Sahih al-Bukhari 48
صحيح البخاري#48Sahihحَدَّثَنَا مُحَمَّدُ بْنُ عَرْعَرَةَ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ زُبَيْدٍ، قَالَ سَأَلْتُ أَبَا وَائِلٍ عَنِ الْمُرْجِئَةِ،، فَقَالَ حَدَّثَنِي عَبْدُ اللَّهِ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ " سِبَابُ الْمُسْلِمِ فُسُوقٌ، وَقِتَالُهُ كُفْرٌ ".
Narrated 'Abdullah: The Prophet (ﷺ) said, "Abusing a Muslim is Fusuq (an evil doing) and killing him is Kufr (disbelief)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 2:41