Sahih al-Bukhari 1178
صحيح البخاري#1178SahihNarrated Abu Huraira:My friend (the Prophet) advised me to do three things and I shall not leave them till I die, these are: To fast three days every month, to offer the Duha prayer, and to offer witr before sleeping
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: 19:56