Sahih Muslim
The Book of Sacrifices (Kitab Al-Adahi)
Book Number: 022 / Hadith Number: 4842
Anas reported that Allah's Messenger (may peace be upon him) sacrificed two horned rams of white colour with black markings over them. He also stated: I saw him sacrificing them with his own hand and saw him placing his foot on their sides, and recited the name of Allah and Glorified Him.