Sunan an-Nasa'i, Volume 2, Book 20, Hadith 1741 (DarusSalam) ⓘ

Muhammad bin Bashshar informed us, he said: "Abu Dawud narrated to us from Shu'bah, from Qatadah, who said: I heard 'Azarah narrating from Sa'eed bin 'Abdur-Rahman Ibn Abza, from his father That the Messenger of Allah used to recite in witr: Glorify the Name of your Lord, the Most High;" and "Say: O you disbelievers!;' and 'Say: He is Allah, (the) One.' And when he had finished praying, he said: Subhanal-Malikil-Quddus (Glory be to the Sovereign, the Most Holy) three times."

أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا أَبُو دَاوُدَ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، قَالَ سَمِعْتُ عَزْرَةَ، يُحَدِّثُ عَنْ سَعِيدِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ أَبْزَى، عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يُوتِرُ بِـ ‏{‏ سَبِّحِ اسْمَ رَبِّكَ الأَعْلَى ‏}‏ وَ ‏{‏ قُلْ يَا أَيُّهَا الْكَافِرُونَ ‏}‏ وَ ‏{‏ قُلْ هُوَ اللَّهُ أَحَدٌ ‏}‏ فَإِذَا فَرَغَ قَالَ ‏"‏ سُبْحَانَ الْمَلِكِ الْقُدُّوسِ ‏"‏ ‏.‏ ثَلاَثًا ‏.‏