It was narrated from Abu Musa that the Messenger of Allah ﷺ said:
“When two Muslims confront one another with their swords, both the killer and the slain will be in Hell.” They said: “O Messenger of Allah, (we understand about) this killer, but what is wrong with the one who is slain?” He said: “He wanted to kill his companion.’”

حَدَّثَنَا أَحْمَدُ بْنُ سِنَانٍ، حَدَّثَنَا يَزِيدُ بْنُ هَارُونَ، عَنْ سُلَيْمَانَ التَّيْمِيِّ، وَسَعِيدِ بْنِ أَبِي عَرُوبَةَ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، عَنْ أَبِي مُوسَى، قَالَ قَالَ رَسُولُ اللَّهِ ـ ﷺ ـ " إِذَا الْتَقَى الْمُسْلِمَانِ بِسَيْفَيْهِمَا فَالْقَاتِلُ وَالْمَقْتُولُ فِي النَّارِ " . قَالُوا يَا رَسُولَ اللَّهِ هَذَا الْقَاتِلُ فَمَا بَالُ الْمَقْتُولِ قَالَ " إِنَّهُ أَرَادَ قَتْلَ صَاحِبِهِ " .