Jami` at-Tirmidhi 468
جامع الترمذي#468Sahihحَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ الْخَلاَّلُ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، عَنْ أَبِي نَضْرَةَ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَوْتِرُوا قَبْلَ أَنْ تُصْبِحُوا " .
Abu Sa'eed Al-Khudri narrated that :Allah's Messenger said: "Perform Witr before the morning comes upon you
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 3:16