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.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
tabarani:9409 – Muḥammad b. al-Naḍr al-Azdī > Muʿāwiyah b. ʿAmr > Zāʾidah > Abū Ḥuṣayn al-Asadī > al-Aswad b. Hilāl > ʿAbdullāh b. Masʿūd

[Machine] "The period between the two prayers is considered to be a voluntary prayer, and specifically the period between the Isha (Night) prayer and the Fajr (Dawn) prayer."  

الطبراني:٩٤٠٩ – حَدَّثَنَا مُحَمَّدُ بْنُ النَّضْرِ الْأَزْدِيُّ ثنا مُعَاوِيَةُ بْنُ عَمْرٍو ثنا زَائِدَةُ ثنا أَبُو حُصَيْنٍ الْأَسَدِيُّ عَنِ الْأَسْوَدِ بْنِ هِلَالٍ عَنْ عَبْدِ اللهِ بْنِ مَسْعُودٍ قَالَ

«مَا بَيْنَ الصَّلَاتَيْنِ وِتْرٌ مَا بَيْنَ صَلَاةِ الْعِشَاءِ وَصَلَاةِ الْفَجْرِ»  

See similar narrations below:

Collected by Ṭabarānī, Suyūṭī
tabarani:9408 – ʿAlī b. ʿAbd al-ʿAzīz > Abū Nuʿaym > Sharīk > Ashʿath b. Abū al-Shaʿthāʾ And ʾAbī Ḥuṣayn Waʿayyāsh al-ʿĀmirī > al-Aswad b. Hilāl

[Machine] Abdullah said, "Al-Witr is the prayer that is performed between Isha prayer and Fajr prayer."  

الطبراني:٩٤٠٨ – حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ الْعَزِيزِ ثنا أَبُو نُعَيْمٍ ثنا شَرِيكٌ عَنْ أَشْعَثَ بْنِ أَبِي الشَّعْثَاءِ وَأَبِي حُصَيْنٍ وَعَيَّاشٍ الْعَامِرِيِّ عَنِ الْأَسْوَدِ بْنِ هِلَالٍ قَالَ قَالَ

عَبْدُ اللهِ «الْوِتْرُ مَا بَيْنَ الصَّلَاتَيْنِ صَلَاةِ الْعِشَاءِ وَصَلَاةِ الْفَجْرِ»