Musnad Ahmad 1012:12

Sufyan ibn 'Uyaynah narrated to us, from al-Zuhri, from Mahmud ibn al-Rabi', from 'Ubadah ibn al-Samit, in a narration he attributes to the Prophet, may God bless him and grant him peace: "There is no prayer for the one who does not recite the Opening of the Book (al-Fatihah)."