The Rites of Hajj (Kitab Al-Manasik Wa'l-Hajj)
Dawud :: Book 10 : Hadith 1829
Narrated Aisha, Ummul Mu'minin:
Riders would pass us when we accompanied the Apostle of Allah (peace_be_upon_him) while we were in the sacred state (wearing ihram). When they came by us, one of us would let down her outer garment from her head over her face, and when they had passed on, we would uncover our faces.