Sahih Muslim
The Book of Pilgrimage (Kitab Al-Hajj)
Book Number: 007 / Hadith Number: 2940
Muhammad b. Abu Bakr reported: I said to Anas b. Malik in the morning of 'Arafa: What do you say as to pronouncing Talbiya on this day? He said: I travelled with Allah's Apostle (may peace he upon him) and his Companions in this journey. Some of us pronounced Takbir and some of us pronounced Tahlil, and none of us found fault with his companion.