Sahih al-Bukhari 994
صحيح البخاري#994SahihNarrated `A'isha:Allah's Messenger (ﷺ) used to pray eleven rak`at at night and that was his night prayer and each of his prostrations lasted for a period enough for one of you to recite fifty verses before Allah's Messenger (ﷺ) raised his head. He also used to pray two rak`at (Sunnah) before the (compulsory) Fajr prayer and then lie down on his right side till the Mu'adh-dhin came to him 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: 14:5