Sunan Abi Dawud 1423
سنن أبي داود#1423SahihNarrated Ubayy ibn Ka'b: The Messenger of Allah (ﷺ) 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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Zubair Ali ZaiHasan
In-book reference: 8:8