Sahih Muslim Book 7, Hadith Number 2779.

Chapter : Types of Ihram- It is permissible to enter into the state of Ihram singularly for the sake of Hajj or for tamattu’ bi’l-‘umra ila’l-Hajj or for both hajj and ‘umra together.

‘Umra reported: I heard ‘Aisha (Allah be pleased with her) as saying: We went out with the Messenger of Allah (may peace be upon him) five days before the end of Dhi Qa’dah, and we did see but that he intended to perform Hajj (only), but as we came near Mecca the Messenger of Allah (may peace be upon him) commanded that he who did not have the sacrificial animal with him should put off Ihram after circumambulating the House and running between al-Safa and aI-Marwa (and thus convert his Ihram from that of Hajj to ‘Umra). ‘Aisha (Allah be pleased with her) said: The flesh of cow was sent to us on the Day of Sacrifice (10th of Dhu’I-Hijja). I said. What is this? It was said: The Messenger of Allah (may peace be upon him) sacrificed (the cow) on behalf of his wives. Yabyi said: I made a mention of this Hadith (what has been stated by Umra) to Qisim b. Muhammad, whereupon be said: By Allah, she has rightly narrated it to you.