كتاب الصلاة
2
The Book of Prayer
Narrated 'Abdullah bin Buraidah (RA) from his father:
Allah's Messenger (ﷺ) said: "The Witr is a duty, so he who does not offer it, is not one of us." [Reported by Abu Dawud with a Laiyin (weak) chain of narrators and Al-Hakim graded it Sahih (authentic)].
وَعَنْ عَبْدِ اَللَّهِ بْنِ بُرَيْدَةَ , عَنْ أَبِيهِ قَالَ : قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ اَلْوِتْرُ حَقٌّ, فَمَنْ لَمْ يُوتِرْ فَلَيْسَ مِنَّا } أَخْرَجَهُ أَبُو دَاوُدَ بِسَنَد لَيِّنٍ, وَصَحَّحَهُ اَلْحَاكِمُ .‏ 1‏ .‏


‏1 ‏- ضعيف.‏ رواه أبو داود (1419)‏، والحاكم (1/305‏-306)‏.‏

Sunnah.com reference : Book 2, Hadith 279
English reference : Book 2, Hadith 370
Arabic reference : Book 2, Hadith 375