Sahih Muslim Book 7, Hadith Number 2676.

Chapter : Entering upon the state of Ihram as the ride proceeds towards (Mecca).

Ibn ‘Umar (Allah be pleased with them) reported that the Messenger of Allah (may peace be upon him) pronounced Talbiya in Dhu’l-Hulaifa as he put his feet in the stirrup and his camel stood up and proceeded.