From Sahih Bukhari (Hadith 4520):
Narrated `Aisha:The Quraish people and those who embraced their religion, used to stay at Muzdalifa and used to call themselves Al-Hums, while the rest of the Arabs used to stay at `Arafat. When Islam came, Allah ordered His Prophet to go to `Arafat and stay at it, and then pass on from there, and that is what is meant by the Statement of Allah:--"Then depart from the place whence all the people depart
Reference: Bukhari 4520