أَخْبَرَنَا أَحْمَدُ بْنُ حَرْبٍ، قَالَ حَدَّثَنَا قَاسِمٌ، عَنْ سُفْيَانَ، عَنْ زُبَيْدٍ، عَنْ سَعِيدِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ أَبْزَى، عَنْ أَبِيهِ، عَنِ النَّبِيِّ صلى الله عليه وسلم أَنَّهُ كَانَ يُوتِرُ بِـ { سَبِّحِ اسْمَ رَبِّكَ الأَعْلَى } وَ { قُلْ يَا أَيُّهَا الْكَافِرُونَ } وَ { قُلْ هُوَ اللَّهُ أَحَدٌ } وَيَقُولُ بَعْدَ مَا يُسَلِّمُ " سُبْحَانَ الْمَلِكِ الْقُدُّوسِ " . ثَلاَثَ مَرَّاتٍ يَرْفَعُ بِهَا صَوْتَهُ .
It was narrated from Ibn Abdur-Rahman bin Abza from his father that: The Messenger of Allah (PBUH) 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 after he had said the salam, he would say: Subhanal-Malikil-Quddus (Glory be to the Sovereign, the Most Holy) raising his voice the third time." Translation Not Available
Book Ref: Sunan An Nisai Book 20 Hadith 1750
Web Ref: Sunan An Nisai Vol 2 Book 20 Hadith 1751