أَخْبَرَنَا مَحْمُودُ بْنُ غَيْلاَنَ، قَالَ حَدَّثَنَا أَبُو دَاوُدَ، عَنْ شُعْبَةَ، قَالَ أَخْبَرَنِي مَنْصُورٌ، قَالَ سَمِعْتُ رِبْعِيًّا، يُحَدِّثُ عَنْ أَبِي بَكْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِذَا أَشَارَ الْمُسْلِمُ عَلَى أَخِيهِ الْمُسْلِمِ بِالسِّلاَحِ فَهُمَا عَلَى جُرُفِ جَهَنَّمَ فَإِذَا قَتَلَهُ خَرَّا جَمِيعًا فِيهَا ‏"‏ ‏.‏

It was narrated that Abu Bakrah said: "The Messenger of Allah [SAW] said: 'If a Muslim points a weapon at his fellow Muslim, then they are on the brink of Hell, and if he kills him, then they will both fall into it.'" Translation Not Available

Book Ref: Sunan An Nisai Book 37 Hadith 4116
Web Ref:  Sunan An Nisai Vol 5 Book 37 Hadith 4121