Abu Dawud Book 2, Hadith Number 1434.
Chapter : The witr is not to be repeated.
Narated By Talq ibn Ali : Qays ibn Talq said: Talq ibn Ali visited us on a certain day during Ramadan. He remained with us till evening and broke fast with us. He then stood up and led us in the witr prayer.
He then went to his mosque and led them in prayer. When the witr remained, he put forward another man and said: Lead your companions in the witr prayer, for I heard the Apostle of Allah (PBUH) as saying: There are no two witrs during one night.