(28) باب بَيَانِ قَوْلِ النَّبِيِّ صلى الله عليه وسلم " سِبَابُ الْمُسْلِمِ فُسُوقٌ وَقِتَالُهُ كُفْرٌ "
Abu Bakr b. Abu Shaiba narrated a hadith like this from the Apostle (may peace and blessings be upon him) on the authority of Abdullah. (ID)
Reference (ID): Sahih Muslim 64 b (ID)
In-book reference (ID): Book 1, Hadith 128 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 1, Hadith 123 (ID)