Sahih al-Bukhari 634
صحيح البخاري#634SahihNarrated `Aun bin Abi Juhaifa:My father said, "I saw Bilal turning his face from side to side while pronouncing the Adhan for the prayer
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: 10:31