Sahih al-Bukhari 1318
صحيح البخاري#1318SahihNarrated Abu Huraira:The Prophet (ﷺ) informed his companions about the death of An-Najashi and then he went ahead (to lead the prayer) and the people lined up behind him in rows and he said four Takbir
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: 23:75