Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1569
'A'isha reported that the Messenger of Allah (may peace be upon him) observed two rak'ahs of the dawn prayer and he shortened them (to the extent) that I (out of surprise) said: Did he recite in them Surah Fatiha (only)?