Maliks Muwatta Book 20, Hadith Number 184.
Section : Sending Women and Children Ahead.
Yahya related to me from Malik from Hisham ibn Urwa that Fatima bint al-Mundhir told him that she used to see Asma bint Abi Bakrat Muzdalifa telling whoever led the subh prayer for her and her companions to pray it as soon as the dawn broke, after which she would mount and go to Mina without stopping at all.