Sunan an-Nasa'i 1702
سنن النسائي#1702SahihZakariyya bin Abi Za'idah narrated from Abu Ishaq, from Sa'id bin Jubair, that Ibn Abbas said:"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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 20:105