Abu Mu'aid narrated from Az-Zuhri, who said:"Ata' bin Yazid narrated to me that he heard Abu Ayyub Al-Ansari say: 'Witr is a duty, so whoever wants to pray witr with five rak'ahs 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