Sahih Bukhari Volume 002, Book 026, Hadith Number 739.
Narated By 'Abdullah : (The slave of Asma') During the night of Jam', Asma' got down at Al-Muzdalifa and stood up for (offering) the prayer and offered the prayer for some time and then asked, "O my son! Has the moon set?" I replied in the negative and she again prayed for another period and then asked, "Has the moon set?" I replied, "Yes." So she said that we should set out (for Mina), and we departed and went on till she threw pebbles at the Jamra (Jamrat-al-Aqaba) and then she returned to her dwelling place and offered the morning prayer. I asked her, "O you! I think we have come (to Mina) early in the night." She replied, "O my son! Allah's Apostle gave permission to the women to do so."