It was narrated from ‘Abd ar-Rahmaan ibn Abza (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) used to recite in Witr
“Sabbih isma Rabbika al-A’la (Glorify the name of your Lord, the Most High)…” [i.e., Soorat al-A’laa 87] and Qul yaa ayyuha’l-kaafiroon (Say (O Muhammad), ‘O al-Kaafiroon (disbelievers))…’” [i.e., Soorat al-Kaafiroon 109] and “Qul Huwa Allaahu ahad (Say (O Muhammad), ‘He is Allaah, (the) One)…” [i.e., Soorat al-Ikhlaas 112].
And after he said the tasleem he would say
“Subhaan al-Malik al-Quddoos, Subhaan al-Malik al-Quddoos
(Glory be to the Sovereign, the Most Holy)”,
three times, raising his voice the third time.