مُوَطَّأُ مَالِكٍ
Muwatta Malik 271
Tahajjud
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ رَجُلاً، سَأَلَ عَبْدَ اللَّهِ بْنَ عُمَرَ عَنِ الْوِتْرِ أَوَاجِبٌ هُوَ فَقَالَ عَبْدُ اللَّهِ بْنُ عُمَرَ قَدْ أَوْتَرَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَأَوْتَرَ الْمُسْلِمُونَ . فَجَعَلَ الرَّجُلُ يُرَدِّدُ عَلَيْهِ وَعَبْدُ اللَّهِ بْنُ عُمَرَ يَقُولُ أَوْتَرَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَأَوْتَرَ الْمُسْلِمُونَ .
Yahya related to me from Malik that he had heard that a man asked Abdullah ibn Umar whether the witr was obligatory and Abdullah ibn Umar said, "The Messenger of Allah, (ﷺ), prayed witr, and the muslims prayed witr." The man began repeating his question, and Abdullah ibn Umar kept saying, "The Messenger of Allah, (ﷺ), prayed witr, and the muslims prayed witr."
Arabic/English book reference: Book 7, Hadith 17