Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) used to pray witr with three surahs: "Glorify the name of your Lord, the Most High" [Surah al-A'la: 1], "Say: O disbelievers" [Surah al-Kafirun: 1] and "Say: He is Allah, the One" [Surah al-Ikhlas: 1], and he would recite the qunut before the bowing. When he gave the salam he would say: 'Subhan al-Malik al-Quddus' (Glory be to the King, the Most Holy) three times, and at the end he would raise his voice and say: 'Rabb al-mala'ikati wa al-ruh' (Lord of the angels and the Spirit).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4862