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:4119 – Muḥammad b. Ismāʿīl b. Ibrāhīm > Yazīd / Ibn Hārūn > Saʿīd > Qatādah > al-Ḥasan > Abū Mūsá al-Ashʿarī

The Prophet [SAW] said: "If two Muslims confront each other with swords and one of them kills the other, they will both be in Hell."  

النسائي:٤١١٩ – أَخْبَرَنِي مُحَمَّدُ بْنُ إِسْمَاعِيلَ بْنِ إِبْرَاهِيمَ قَالَ حَدَّثَنَا يَزِيدُ وَهُوَ ابْنُ هَارُونَ قَالَ أَنْبَأَنَا سَعِيدٌ عَنْ قَتَادَةَ عَنِ الْحَسَنِ عَنْ أَبِي مُوسَى الأَشْعَرِيِّ

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا تَوَاجَهَ الْمُسْلِمَانِ بِسَيْفَيْهِمَا فَقَتَلَ أَحَدُهُمَا صَاحِبَهُ فَهُمَا فِي النَّارِ مِثْلَهُ سَوَاءً  

See similar narrations below:

Collected by Nasāʾī
nasai:4121 – Muḥammad b. al-Muthanná > al-Khalīl b. ʿUmar b. Ibrāhīm from my father > Qatādah > al-Ḥasan > Abū Bakrah

"The Messenger [SAW] said: 'If two Muslims meet (and fight) with their swords and one of them kills the other, the killer and the slain will both be in Hell.'"  

النسائي:٤١٢١ – أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى قَالَ حَدَّثَنَا الْخَلِيلُ بْنُ عُمَرَ بْنِ إِبْرَاهِيمَ قَالَ حَدَّثَنِي أَبِي قَالَ حَدَّثَنِي قَتَادَةُ عَنِ الْحَسَنِ عَنْ أَبِي بَكْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا الْتَقَى الْمُسْلِمَانِ بِسَيْفَيْهِمَا فَقَتَلَ أَحَدُهُمَا صَاحِبَهُ فَالْقَاتِلُ وَالْمَقْتُولُ فِي النَّارِ  

nasai:4123 – Aḥmad b. ʿAbdah > Ḥammād > Ayyūb And Yūnus Wa-al-ʿAlāʾ b. Ziyād > al-Ḥasan > al-Aḥnaf b. Qays > Abū Bakrah

"The Messenger of Allah [SAW] said: 'If two Muslims fight with swords, and one of them kills the other, then the killer and the slain will both be in Hell.'"  

النسائي:٤١٢٣ – أَخْبَرَنَا أَحْمَدُ بْنُ عَبْدَةَ عَنْ حَمَّادٍ عَنْ أَيُّوبَ وَيُونُسَ وَالْعَلاَءِ بْنِ زِيَادٍ عَنِ الْحَسَنِ عَنِ الأَحْنَفِ بْنِ قَيْسٍ عَنْ أَبِي بَكْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا الْتَقَى الْمُسْلِمَانِ بِسَيْفَيْهِمَا فَقَتَلَ أَحَدُهُمَا صَاحِبَهُ فَالْقَاتِلُ وَالْمَقْتُولُ فِي النَّارِ