Sahih Muslim Book 007, Hadith Number 2813.
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: The Messenger of Allah (May peace be upon him) had sent me to Yemen and I came back In the year in which he (the Holy Prophet) performed the (Farewell) Pilgrimage. Allah's Messenger (may peace be upon, him) said to me: Abu Musa, what did you ' say when you entered into the state of Ihram? I said: At thy beck and call; my (Ihram) is that of the Ihram of Allah's Apostle (May peace be upon him). He said: Have you brought the sacrificial animals? I said: No. Thereupon he said: Go and circumambulate the House, and (run) between al-Safa' and al-Marwa and then put off Ihram. The rest of the Hadith is the same.