Al-Awza'I said:"Az-Zuhri narrated to me, he said: 'Ata bin Yazid, from Abu Ayyub: The Messenger of Allah (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

English translation · Sunan an-Nasa'i