Sahih Bukhari Volume 002, Book 026, Hadith Number 816.
Narated By 'Abdul-Aziz bin Rufai : I asked Anas bin Malik, "Tell me something you have observed about the Prophet concerning where he offered the Zuhr prayer on the Day of Tarwiya (8th Dhul-Hijja)." Anas replied, "He offered it at Mina." I said, "Where did he offer the Asr prayer on the Day of Nafr (day of departure from Mina)?" He replied, "At Al-Abtah," and added, "You should do as your leaders do."