Al-AwzaI said: "Az-Zuhri narrated to me, he said: Ata bin Yazid, from Abu Ayyub: The Messenger of Allah (صلی اللہ علیہ وسلم) said: Witr is a duty, and whoever wants to pray witr with seven (rakahs), 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."