The Rites of Hajj (Kitab Al-Manasik Wa'l-Hajj)
Dawud :: Book 10 : Hadith 1936
Narrated Abdullah ibn Abbas:
The Apostle of Allah (peace_be_upon_him) used to send ahead the weak members of his family in darkness (to Mina), and command them not to throw pebbles at jamrahs until the sun rose.