Sahih al-Bukhari 472
صحيح البخاري#472SahihNarrated Nafi`:Ibn `Umar said, "While the Prophet (ﷺ) was on the pulpit, a man asked him how to offer the night prayers. He replied, 'Pray two rak`at at a time and then two and then two and so on, and if you are afraid of the dawn (the approach of the time of the Fajr prayer) pray one rak`a and that will be the witr for all the rak`at which you have offered." Ibn `Umar said, "The last rak`at of the night prayer should be odd, for the Prophet (ﷺ) ordered it to be so
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: 8:120