Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
bukhari:6103 – Muḥammad And ʾAḥmad b. Saʿīd > ʿUthmān b. ʿUmar > ʿAlī b. al-Mubārak > Yaḥyá b. Abū Kathīr > Abū Salamah > Abū Hurayrah

Messenger of Allah ﷺ said, "If a man says to his brother, O Kafir (disbeliever)!' Then surely one of them is such (i.e., a Kafir). "  

البخاري:٦١٠٣ – حَدَّثَنَا مُحَمَّدٌ وَأَحْمَدُ بْنُ سَعِيدٍ قَالاَ حَدَّثَنَا عُثْمَانُ بْنُ عُمَرَ أَخْبَرَنَا عَلِيُّ بْنُ الْمُبَارَكِ عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ عَنْ أَبِي سَلَمَةَ عَنْ أَبِي هُرَيْرَةَ ؓ

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِذَا قَالَ الرَّجُلُ لأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهِ أَحَدُهُمَا وَقَالَ عِكْرِمَةُ بْنُ عَمَّارٍ عَنْ يَحْيَى عَنْ عَبْدِ اللَّهِ بْنِ يَزِيدَ سَمِعَ أَبَا سَلَمَةَ سَمِعَ أَبَا هُرَيْرَةَ عَنِ النَّبِيِّ ﷺ