Musnad Ahmad 1153:1965

Yazid narrated to us, Yahya informed us, that Muhammad ibn Abd al-Rahman, the nephew of Amrah, informed him from Amrah, that she heard Aisha saying: The Messenger of Allah (peace and blessings of Allah be upon him) used to pray the two rak'ahs before the dawn prayer, and he would lighten them so much that I would say: "Did he recite the Mother of the Quran (Al-Fatiha) in them?"