Sahih Muslim
The Book of Pilgrimage (Kitab Al-Hajj)
Book Number: 007 / Hadith Number: 3050
Anas reported: Someone happened to pass by Allah's Apostle (may peace be upon him) with a sacrificial camel, or a sacrificial animal, whereupon he said: Ride on it. He said: It is a sacrificial camel, or animal, whereupon he said: (Ride) even if (it is a sacrificial camel).