Sahih al-Bukhari 642
صحيح البخاري#642SahihNarrated Anas:Once the Iqama was pronounced and the Prophet (ﷺ) was talking to a man (in a low voice) in a corner of the mosque and he did not lead the prayer till (some of) the people had slept (dozed in a sitting posture)
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: 10:39