حَدَّثَنَا سُوَيْدُ بْنُ سَعِيدٍ، حَدَّثَنَا مُبَارَكُ بْنُ سُحَيْمٍ، عَنْ عَبْدِ الْعَزِيزِ بْنِ صُهَيْبٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، عَنِ النَّبِيِّ ـ صلى الله عليه وسلم ـ قَالَ ‏"‏ مَا مِنْ مُسْلِمَيْنِ الْتَقَيَا بِأَسْيَافِهِمَا إِلاَّ كَانَ الْقَاتِلُ وَالْمَقْتُولُ فِي النَّارِ ‏"‏ ‏.‏
Translation
It was narrated from Abu Musa that the Messenger of Allah (ﷺ) said

“When two Muslims confront one another with their swords, both thekiller and the slain will be in Hell.” They said: “O Messenger ofAllah, (we understand about) this killer, but what is wrong with theone who is slain?” He said: “He wanted to kill his companion.’”