بُلُوغُ الْمَرَامِ
Bulugh al-Maram 385
The Book of Prayer
وَعَنْ أُبَيِّ بْنِ كَعْبٍ - رضى الله عنه - قَالَ: { كَانَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -يُوتِرُ بِـ "سَبِّحِ اِسْمَ رَبِّكَ اَلْأَعْلَى", و: "قُلْ يَا أَيُّهَا اَلْكَافِرُونَ", و: "قُلْ هُوَ اَللَّهُ أَحَدٌ" } رَوَاهُ أَحْمَدُ, وَأَبُو دَاوُدَ, وَالنَّسَائِيُّ. وَزَادَ: { وَلَا يُسَلِّمُ إِلَّا فِي آخِرِهِنَّ } [1] .
Narrated Ubai bin Ka'b (RA): Allah's Messenger (ﷺ) recited in Witr prayer Surat al-A'la (in the first Rak'at), Surat al-Kafirun (in the second Rak'at) and Surat al-Ikhlas (in the third Rak'at). [Reported by Ahmad, Abu Dawud and an-Nasa'i]. The latter added, "And he did not say the Taslim (salutation) except in the last (Rak'at) of them."
Sunnah.com reference: Book 2, Hadith 289