حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ حَدَّثَنَا سُفْيَانُ عَنْ أَبِي إِسْحَاقَ عَنْ عَاصِمِ بْنِ ضَمْرَةَ عَنْ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ لَيْسَ الْوَتْرُ بِحَتْمٍ كَهَيْئَةِ الصَّلَاةِ وَلَكِنْ سُنَّةٌ سَنَّهَا رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ
مسند امام احمد بن حنبل · Hadith 761
It was narrated that 'Ali (RA) said: Witr is not a must like regular prayer, but it is a Suntmh that was established by the Messenger of Allah (PBUH).
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020