Musnad Ahmad 5:712

Abdullah narrated to us, Abu Bakr ibn Abi Shaybah and Muhammad ibn Ubayd al-Muharibi narrated to me, they said: Sharik narrated to us, from Abu al-Hasna’, from al-Hakam, from Hanash, from Ali, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) commanded me to sacrifice two rams on his behalf, so I love to do it." And Muhammad ibn Ubayd al-Muharibi said in his narration: "He sacrificed two rams on his behalf; one on behalf of the Prophet (peace and blessings of Allah be upon him), and the other on his own behalf." It was said to him [about that], and he said: "He commanded me, so I will never abandon it."