"Abu Dawud narrated to us, he said: Shu'ba narrated to us, from Qatadah, from Abdur-Rahman bin Abza, that The Messenger of Allah ﷺ 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 said the taslim, he would say: Subhanal-Malikil-Quddus (Glory be to the Sovereign, the Most Holy) three times, elongating his words the third time." (Using translation from Nasāʾī 1741)

أَنَّ رَسُولَ اللهِ ﷺ كَانَ يُوتِرُ بِسَبِّحِ اسْمَ رَبِّكِ الْأَعْلَى وَقُلْ يَا أَيُّهَا الْكَافِرُونَ وَقُلْ هُوَ اللهُ أَحَدٌ فَإِذَا فَرَغَ قَالَ سُبْحَانَ الْمَلِكِ الْقُدُّوسِ ثَلَاثًا مَدَّ الصَّوْتَ بِالتَّسْبِيحِ فِي الثَّالِثَةِ

[Machine] The Messenger of Allah ﷺ used to perform Witr by reciting: “Glorify the Name of your Lord, the Most High” (Sūrat al-Aʿlā), “Say: O disbelievers” (Sūrat al-Kāfirūn), and “Say: He is Allah, One” (Sūrat al-Ikhlāṣ). Then, when he finished with the salām, he would say, “Glory be to the Sovereign, the Most Holy,” three times, and he would prolong it on the third time.

أَنَّ رَسُولَ اللهِ ﷺ كَانَ يُوتِرُ بِسَبِّحِ اسْمَ رَبِّكَ الْأَعْلَى وَقُلْ يَا أَيُّهَا الْكَافِرُونَ وَقُلْ هُوَ اللهُ أَحَدٌ فَإِذَا سَلَّمَ قَالَ سُبْحَانَ الْمَلِكِ الْقُدُّوسِ ثَلَاثًا وَيَمُدُّهَا فِي الثَّالِثَةِ