Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1346
'A'isha, the wife of the Apostle of Allah (may peace be upon him), reported: The believing women observed the morning prayer with the Messenger of Allah (may peace be upon him) wrapped in their mantles. They then went back to their houses and were unrecognisable, because of the Messenger of Allah's (may peace be upon him) praying in the darkness before dawn.