Sahih al-Bukhari 1326
صحيح البخاري#1326SahihNarrated 'Amir:Ibn `Abbas (who was at that time a boy) said, "Allah's Messenger (ﷺ) came to a grave and the people said, 'He or she was buried yesterday.' " Ibn `Abbas added, "We aligned behind the Prophet (ﷺ) and he led the funeral prayer of the deceased
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: 23:82