Musnad Ahmad 594:6

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Shamir ibn 'Atiyyah, from Hilal ibn Yasaf, from Wabisa ibn Ma'bad, who said: The Messenger of Allah, peace and blessings of Allah be upon him, was asked about a man who prayed behind the rows alone. He said: "He shall repeat the prayer."