Abu Musa (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) had sent me to Yemen, and I met him (peace and blessings be upon him) in the year in which he (peace and blessings be upon him) performed Hajj. He (peace and blessings be upon him) said to me: "O Abu Musa! What did you say when you entered ihram?" I said: I made the intention to do as the Prophet (peace and blessings be upon him) did. He (peace and blessings be upon him) asked: "Have you brought a sacrificial animal?" I said: No. He (peace and blessings be upon him) said: "Go, perform tawaf of the House (the Ka'bah) and sa'i between Safa and Marwah, then come out of ihram." So I went, performed tawaf of the House and sa'i between Safa and Marwah, then I went to some women of the family of Qays, that is, my paternal aunts, and they washed my head and combed it. Then after that, during the caliphate of Umar (may Allah be pleased with him), I came to perform Hajj. While I was telling the people what the Messenger of Allah (peace and blessings be upon him) had told me, a man came and said: Be careful with this talk of yours; do you not know what the Commander of the Believers has introduced in the rites of Hajj? So I said: O people! Whoever has heard anything, let him not act on it until the Commander of the Believers arrives; follow him. When Umar (may Allah be pleased with him) arrived, I said: Has some new ruling been issued regarding the way of Hajj? Umar (may Allah be pleased with him) became angry at this, then said: Yes; if we take the Book of Allah, Allah Almighty has commanded completion; and if we take (the Sunnah of) the Messenger of Allah (peace and blessings be upon him), he (peace and blessings be upon him) did not come out of ihram before offering the sacrifice.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8687