Sunan an-Nasa'i 4117
سنن النسائي#4117SahihIt was narrated that Abu Bakrah said:"If two Muslim men bear weapons against each other, then they are both on the brink of Hell. And if one of them kills the other, they will both be in Hell
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih Muquf
Al-AlbaniSahih Muquf
Zubair Ali ZaiHasan
In-book reference: 37:152