Musnad Ahmad 2:192

'Abd al-Rahman narrated to us, Sufyan narrated to us, from Qays ibn Muslim, from Tariq ibn Shihab, from Abu Musa, who said: I arrived to the Messenger of Allah (peace and blessings of Allah be upon him) while he was at al-Batha. He said: "With what did you enter into Ihram?" I said: "With an Ihram like the Ihram of the Prophet (peace and blessings of Allah be upon him)." He said: "Did you bring any sacrificial animal (Hady)?" I said: "No." He said: "Perform Tawaf around the House and between al-Safa and al-Marwa, then exit Ihram." So I performed Tawaf around the House and between al-Safa and al-Marwa, then I went to a woman from my people, and she combed my hair and washed my head. I continued to give this fatwa to the people during the leadership of Abu Bakr and the leadership of Umar. While I was standing at the season (of Hajj), a man came to me and said: "You do not know what the Commander of the Believers has introduced regarding the matter of the rituals." I said: "O people, whoever we have given a fatwa to, this is the Commander of the Believers arriving to you, so follow him." When he arrived, I said: "What is this that you have introduced regarding the matter of the rituals?" He said: "We take by the Book of Allah, for Allah said: 'And complete the Hajj and 'Umrah for Allah' [Al-Baqarah: 196]. And we take by the Sunnah of our Prophet (peace and blessings of Allah be upon him), for he did not exit Ihram until he slaughtered the sacrificial animal."