" Ibn Shihab informed me, saying: 'Ata bin Yazid narrated to me from Abu Ayyub: That the Prophet ﷺ said: 'Witr is a duty, and whoever wants to pray witr with seven (rak'ahs), let him do so; whoever wants to pray witr with five, let him do so, whoever wants to pray witr with three, let him do so; and whoever wants to pray witr with one, let him do so.'" (Using translation from Nasāʾī 1710)  

أَنَّ النَّبِيَّ ﷺ قَالَ «الْوِتْرُ حَقٌّ فَمَنْ شَاءَ أَوْتَرَ بِسَبْعٍ وَمَنْ شَاءَ أَوْتَرَ بِخَمْسٍ وَمَنْ شَاءَ أَوْتَرَ بِثَلَاثٍ وَمَنْ شَاءَ أَوْتَرَ بِوَاحِدَةٍ» وَقَفَهُ أَبُو مُعَيْدٍ  

[Machine] We have Abu Abdul Rahman, also known as Abu Mu'aid, his name is Hafs ibn Ghailan and he is proficient in Hadith.  

لنا أَبُو عَبْدِ الرَّحْمَنِ أَبُو مُعَيْدٍ اسْمُهُ حَفْصُ بْنُ غَيْلَانَ وَهُوَ صَالِحُ الْحَدِيثِ