حَدَّثَنَا مُحَمَّدُ بْنُ فُضَيْلٍ حَدَّثَنَا مُطَرِّفٌ عَنْ أَبِي إِسْحَاقَ عَنْ عَاصِمٍ عَنْ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُوتِرُ فِي أَوَّلِ اللَّيْلِ وَفِي وَسَطِهِ وَفِي آخِرِهِ ثُمَّ ثَبَتَ لَهُ الْوَتْرُ فِي آخِرِهِ
مسند امام احمد بن حنبل · Hadith 580
it was narrated that 'Ali (RA) said: The Messenger of Allah (PBUH) used to pray Witr at the beginning of the night and in the middle and at the end, then he persisted in praying it at the end of the night.
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020