Musnad Abu Ya'la al-Mawsili 115:277

Al-Hakam ibn Musa Abu Salih narrated to us, Abu Mu'awiyah narrated to us, from al-Hajjaj, from Qatadah, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) sacrificed two horned, black-and-white rams. He brought one of them forward and said: "In the name of Allah, O Allah, from You and to You; this is on behalf of Muhammad and the people of his house." Then he brought the other forward and said: "In the name of Allah, O Allah, from You and to You; this is on behalf of whoever among my nation has affirmed Your Oneness."