Sunan An-Nasa'i

It was narrated from Ubayy bin Ka'b that: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"". And he would say the Qunut before bowing, and when he finished he would say: Subhanal-Malikil-Quddus (Glory be to the Sovereign, the Most Holy) three times, elongating the words the last time