Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
abudawud:1419Ibn al-Muthanná > Abū Isḥāq al-Ṭālqānī > al-Faḍl b. Mūsá > ʿUbaydullāh b. ʿAbdullāh al-ʿAtakī > ʿAbdullāh b. Buraydah from his father

I heard the Messenger of Allah ﷺ say: The witr is a duty, so he who does not observe it does not belong to us; the witr is a duty, so he who does not observe it does not belong to us; the witr is a duty, so he who does not observe it does not belong to us.  

أبو داود:١٤١٩حَدَّثَنَا ابْنُ الْمُثَنَّى حَدَّثَنَا أَبُو إِسْحَاقَ الطَّالْقَانِيُّ حَدَّثَنَا الْفَضْلُ بْنُ مُوسَى عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ الْعَتَكِيِّ عَنْ عَبْدِ اللَّهِ بْنِ بُرَيْدَةَ عَنْ أَبِيهِ قَالَ

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ الْوِتْرُ حَقٌّ فَمَنْ لَمْ يُوتِرْ فَلَيْسَ مِنَّا الْوِتْرُ حَقٌّ فَمَنْ لَمْ يُوتِرْ فَلَيْسَ مِنَّا الْوِتْرُ حَقٌّ فَمَنْ لَمْ يُوتِرْ فَلَيْسَ مِنَّا