Sahih Muslim
The Book of Pilgrimage (Kitab Al-Hajj)
Book Number: 007 / Hadith Number: 3049
Anas reported that Allah's Messenger (may peace be upon him) happened to pass by a person who was driving a sacrificial camel, whereupon he (the Holy Prophet) said: Ride on It. He said: It is a sacrificial camel. Thereupon he (the Holy Prophet) said twice or thrice: Ride on it.