حَدَّثَنَا يَزِيدُ أَخْبَرَنَا هِشَامٌ عَنْ مُحَمَّدٍ عَنِ ابْنِ عُمَرَ عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنَّهُ قَالَ صَلَاةُ الْمَغْرِبِ وِتْرُ النَّهَارِ فَأَوْتِرُوا صَلَاةَ اللَّيْلِ
مسند امام احمد بن حنبل · Hadith 4992
It was narrated from Ibn Umar, from the prophet (PBUH) that he said: "Maghrib prayer makes the prayers of the day odd-numbered so make the prayers of the night odd-numbered (by praying Witr)."
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020