Narrated 'Ali bin Abi Talib (RA):

Allah's Messenger (ﷺ) said: "O people of the Qur'an! Offer Witr (prayer), because Allah is Witr (One) and loves Witr." [Reported by al-Khamsah and Ibn Khuzaimah graded it Sahih (authentic)].

وَعَنْ عَلِيٍّ ‏- رضى الله عنه ‏- قَالَ: قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ أَوْتِرُوا يَا أَهْلُ اَلْقُرْآنَ, فَإِنَّ اَللَّهَ وِتْرٌ يُحِبُّ اَلْوِتْرَ } رَوَاهُ اَلْخَمْسَةُ, وَصَحَّحَهُ اِبْنُ خُزَيْمَةَ .‏ [1]‏ .‏