Sahih al-Bukhari 1138
صحيح البخاري#1138SahihNarrated Ibn `Abbas:The prayer of the Prophet (ﷺ) used to be of thirteen rak`at, i.e. of the night 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: 19:19