Sahih Muslim Book 007, Hadith Number 2812.
Chapter : Permissibility of saying one has entered into Ihram like the Ihram of the other one or Abrogation of putting off Ihram and completing (Hajj and Umra).
Abu Musa (Allah be pleased with him) reported: I came to the Messenger of Allah (may peace be upon him) and he was encamping at Batha. He (the Holy Prophet) said: With what purpose have you entered into the state of Ihram? I said: I have entered into the state of Ihram in accordance with the Ihram of Allah's Apostle (may peace be upon him). He said: Have you brought sacrificial animals along with you? I said: No. whereupon he said: Then circumambulate the House and run between al-Safa' and al-Marwa and put off Ihram. So I circumambulated the House, ran between al-Safa' and al-Marwa, and then came to a woman of my tribe. She combed and washed my head. I used to give religious verdict (according to the above mentioned command of the Holy Prophet) during the Caliphate of Abu Bakr and also during that of 'Umar. And it was during the Hajj season that a person came to me and said: You (perhaps) do not know what the Commander of the Believers has introduced in the rites (of Hajj). I said: O people, those whom we have given religious verdict about a certain thing should wait, for the Commander of the Believers is about to arrive among you, so follow him. When the Commander of the Believers arrived, I said: What is this that you have introduced in the rites (of Hajj)? -where upon he said: If we abide by the Book of Allah (we find) that there Allah, Exalted and Majestic, has said: Complete Hajj and 'Umra for Allah." And if we abide by the Sunnah of our Apostle (may peace be upon him) (we find) that the Apostle of Allah (May peace be upon him) did not put off Ihram till he had sacrificed the animals.