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
nasai:4106 – Yaḥyá b. Ḥakīm > ʿAbd al-Raḥman b. Mahdī > Shuʿbah > Abū Isḥāq > Abū al-Aḥwaṣ > ʿAbdullāh > Sibāb al-Muslim Fisq And Qitāluh Kufr

"I heard Abu Al-Ahwas (narrate) that 'Abdullah said: 'Defaming a Muslim is evildoing and fighting him is Kufr.'" So Aban said to him: "O Abu Ishaq! You heard it only from Abu Al-Ahwas?" He said: "Rather, I heard it from Al-Aswad and Hubairah."  

النسائي:٤١٠٦ – أَخْبَرَنَا يَحْيَى بْنُ حَكِيمٍ قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ عَنْ شُعْبَةَ عَنْ أَبِي إِسْحَاقَ عَنْ أَبِي الأَحْوَصِ عَنْ عَبْدِ اللَّهِ قَالَ

سِبَابُ الْمُسْلِمِ فِسْقٌ وَقِتَالُهُ كُفْرٌ فَقَالَ لَهُ أَبَانُ يَا أَبَا إِسْحَاقَ أَمَا سَمِعْتَهُ إِلاَّ مِنْ أَبِي الأَحْوَصِ قَالَ بَلْ سَمِعْتُهُ مِنَ الأَسْوَدِ وَهُبَيْرَةَ  

See similar narrations below:

Collected by Nasāʾī's Kubrá
nasai-kubra:3556 – Yaḥyá b. Ḥakīm > ʿAbd al-Raḥman b. Mahdī > Shuʿbah > Abū Isḥāq > Abū al-Aḥwaṣ > ʿAbdullāh > Sibāb al-Muslim Fusūq And Qitāluh Kufr

"I heard Abu Al-Ahwas (narrate) that 'Abdullah said: 'Defaming a Muslim is evildoing and fighting him is Kufr.'" So Aban said to him: "O Abu Ishaq! You heard it only from Abu Al-Ahwas?" He said: "Rather, I heard it from Al-Aswad and Hubairah." (Using translation from Nasāʾī 4106)   

الكبرى للنسائي:٣٥٥٦ – أَخْبَرَنَا يَحْيَى بْنُ حَكِيمٍ قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ عَنْ شُعْبَةَ عَنْ أَبِي إِسْحَاقَ عَنْ أَبِي الْأَحْوَصِ عَنْ عَبْدِ اللهِ قَالَ «§سِبَابُ الْمُسْلِمِ فُسُوقٌ وَقِتَالُهُ كُفْرٌ» فَقَالَ

لَهُ أَبَانُ يَا أَبَا إِسْحَاقَ أَمَا سَمِعْتَهُ إِلَّا مِنْ أَبِي الْأَحْوَصِ؟ قَالَ بَلَى سَمِعْتُهُ مِنَ الْأَسْوَدِ وَهُبَيْرَةَ