Sahih al-Bukhari 1308
صحيح البخاري#1308SahihNarrated 'Amir bin Rabi`a:The Prophet (ﷺ) said, "If any one of you sees a funeral procession and he is not going along with it, then he should stand and remain standing till he gets behind it, or it leaves him behind, or the coffin is put down before it goes ahead of him
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: 23:66