Musnad Abu Ya'la al-Mawsili 150:99

Ahmad ibn Mani' narrated to us, Marwan narrated to us, from Yahya ibn Sa'id, from Muhammad ibn Yahya ibn Habban, from his paternal uncle, from 'Aishah: That the Prophet, peace and blessings of Allah be upon him, used to pray the two rak'ahs of Fajr and would lighten them, until I would say: "Did he recite the Opening of the Book (Al-Fatihah) in them?"