Sahih Muslim 1729
صحيح مسلم#1729SahihA'isha observed that the Messenger of Allah (ﷺ) used to observe prayer in the night and the last of his (night) prayer was Witr
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 6:158