Sahih al-Bukhari 6868
صحيح البخاري#6868SahihNarrated `Abdullah bin `Umar:The Prophet (ﷺ) said, "After me (i.e. after my death), do not become disbelievers, by striking (cutting) the necks of one another
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 87:7