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). (Using translation from Nasāʾī 1703)
أَنَّ النَّبِيَّ ﷺ كَانَ يُوتِرُ بِثَلاثٍ بِسَبِّحِ اسْمَ رَبِّكَ الْأَعْلَى وَقُلْ يَا أَيُّهَا الْكَافِرُونَ وَقُلْ هُوَ اللهُ أَحَدٌ