Sahih Muslim Book 007, Hadith Number 2958.
Chapter : It is excellent that the aged and the weak, especially among the women, should hasten from Muzdalifa to Mina at the latter part of the night before the people moving in multitude. and excellence of staying there for others until they observe the dawn prayer at Muzdalifa.
'Aisha (Allah be pleased with her) reported: Sauda (the wife of the Holy Prophet) who was bulky sought the permission of Allah's Messenger (may peace be upon him) on the night of Muzdalifa to move from (that place) ahead of him and before the multitude (set forth). He (Allah's Apostle) gave her the permission. So she set forth before his (Holy Prophet's) departure. But we stayed there until it was dawn and we moved on, when he departed. And if I were to seek the permission of Allah's Messenger.(may peace be upon him) as Sauda had sought permission, I could have also gone with his permission and it would have been better for me than that for which I was happy.