"The Messenger of Allah ﷺ used to pray witr with three rak'ahs. In the first he would recite "Glorify the Name of Your Lord, the Most High;" in the second: "Say: O You disbelievers!" and in the third: "Say: He is Allah, (the) One.'"  

كَانَ رَسُولُ اللَّهِ ﷺ يُوتِرُ بِثَلاَثٍ يَقْرَأُ فِي الأُولَى بِ { سَبِّحِ اسْمَ رَبِّكَ الأَعْلَى } وَفِي الثَّانِيَةِ بِ { قُلْ يَا أَيُّهَا الْكَافِرُونَ } وَفِي الثَّالِثَةِ بِ { قُلْ هُوَ اللَّهُ أَحَدٌ } أَوْقَفَهُ زُهَيْرٌ  

Ibn Abbas used to pray witr with three (units) with (the Surahs): "Glorify the Name of Your Lord, the Most High" (Surah Al-A'la), "Say: O You disbelievers" (Surah Al-Kafirun), and "Say: He is Allah, (the) One" (Surah Al-Ikhlas).  

أَنَّهُ كَانَ يُوتِرُ بِثَلاَثٍ بِ { سَبِّحِ اسْمَ رَبِّكَ الأَعْلَى } وَ { قُلْ يَا أَيُّهَا الْكَافِرُونَ } وَ { قُلْ هُوَ اللَّهُ أَحَدٌ }