Jami` at-Tirmidhi 468
جامع الترمذي#468SahihAbu Sa'eed Al-Khudri narrated that :Allah's Messenger said: "Perform Witr before the morning comes upon you
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 3:16