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 three rak'ahs of witr and did not give the salam in between them. In the first rak'ah he recited "Glorify the name of your Lord, the Most High" [Surah al-A'la: 1], in the second rak'ah "Say: O disbelievers" [Surah al-Kafirun: 1], and in the third rak'ah "Say: He is Allah, the One" [Surah al-Ikhlas: 1], and he would recite the qunut before the bowing. When he finished the prayer he would say: 'Subhan al-Malik al-Quddus' (Glory be to the King, the Most Holy), twice quietly and the third time aloud.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4864