Sahih Bukhari Volume 2, Book 26, Hadith Number 721.

Narated By Muhammad bin Abu Bakr Al-Thaqafi : I asked Anas bin Malik while we were proceeding from Mina to ‘Arafat, “What do you use to do on this day when you were with Allah’s Apostle ?” Anas said, “Some of us used to recite Talbiya and nobody objected to that, and others used to recite Takbir and nobody objected to that.”