Sahih Muslim Book 007, Hadith Number 2959.
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 that (hadrat) Sauda was a bulky lady, so she sought permission from Allah's Messenger (may peace be upon him) to proceed from Muzdalifa (to Mina) in the (latter part of the) night. He granted her permission. 'Aisha said: I wish I had also sought permission from Allah's Messenger (may peace be upon him) as Sauda had sought permission from him. 'Aisha did not proceed but with the Imam.