The Messenger of Allah ﷺ used to observe witr with (reciting) "Glorify the name of thy Lord, the most High" (Surah 87), "Say O disbelievers" (Surah 109), and "Say, He is Allah, the One, Allah, the eternally besought of all" (112).  

كَانَ رَسُولُ اللَّهِ ﷺ يُوتِرُ بِ { سَبِّحِ اسْمَ رَبِّكَ الأَعْلَى } وَ { قُلْ لِلَّذِينَ كَفَرُوا } وَاللَّهُ الْوَاحِدُ الصَّمَدُ  

AbdulAziz ibn Jurayj said: I asked Aisha, mother of the believers: With which (surah) the Messenger of Allah ﷺ used to observe witr? (She reported same as in the Hadith of Ubayy ibn Ka'b, No. 1418) This version adds: In the third rak'ah he would recite: "Say, He is Allah, the One" (Surah 112), and "Say, I seek refuge in the Lord of daybreak" (Surah 113), and "Say, I seek refuge in the Lord of mankind" (Surah 114).  

سَأَلْتُ عَائِشَةَ أُمَّ الْمُؤْمِنِينَ بِأَىِّ شَىْءٍ كَانَ يُوتِرُ رَسُولُ اللَّهِ ﷺ فَذَكَرَ مَعْنَاهُ قَالَ وَفِي الثَّالِثَةِ بِ { قُلْ هُوَ اللَّهُ أَحَدٌ } وَالْمُعَوِّذَتَيْنِ