The Book of Prayer
Bulugh al-Maram #450
كتاب الصلاة
وَعَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ - رضى الله عنه - قَالَ: «لَيْسَ اَلْوِتْرُ بِحَتْمٍ كَهَيْئَةِ اَلْمَكْتُوبَةِ, وَلَكِنْ سُنَّةٌ سَنَّهَا رَسُولُ اَللَّهِ - صلى الله عليه وسلم -» رَوَاهُ النَّسَائِيُّ وَاَلتِّرْمِذِيُّ وَحَسَّنَهُ وَالْحَاكِمُ وَصَحَّحَهُ.
Narrated 'Ali bin Abu Talib (RA):
The Witr prayer is not obligatory as the prescribed prayer is, but it is a Sunnah which was established by the practice of Allah's Messenger (ﷺ).
وَعَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ - رضى الله عنه - قَالَ : "لَيْسَ اَلْوِتْرُ بِحَتْمٍ كَهَيْئَةِ اَلْمَكْتُوبَةِ , وَلَكِنْ سُنَّةٌ سَنَّهَا رَسُولُ اَللَّهِ - صلى الله عليه وسلم -" رَوَاهُ النَّسَائِيُّ وَاَلتِّرْمِذِيُّ وَحَسَّنَهُ وَالْحَاكِمُ وَصَحَّحَهُ .
The Witr prayer is not obligatory as the prescribed prayer is , but it is a Sunnah which was established by the practice of Allah's Messenger (ﷺ).
— Bulugh al-Maram, Hadith 450