Sunan an-Nasa'i 4023
سنن النسائي#4023SahihIt was narrated that Usamah bin Sharik said:"The Messenger of Allah [SAW] said: 'Any man who goes out and tries to create division among my Ummah, strike his neck (kill him)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih Lighairihi
Al-AlbaniSahih
Zubair Ali ZaiHasan
In-book reference: 37:58