Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 1418
Narated By Ubayy ibn Ka'b : The Apostle of Allah (pbuh) used to observe witr with (reciting) "Glorify the name of thy Lord, the most High" (Surah 87), "Say O disbelievers" (Surah 109), and "Say, He is Allah, the One, Allah, the eternally besought of all" (112).