Narrated 'Aisha:

We set out in the company of Allah's Apostle five days before the end of Dhul Qa'da intending to perform Hajj only. When we approached Mecca Allah's Apostle ordered those who did not have the Hadi (i.e. an animal for sacrifice) with them, to perform the Tawaf around the Ka'ba, and between Safa and Marwa and then finish their Ihram. Beef was brought to us on the day of (i.e. the days of slaughtering) and I asked, "What is this?" Somebody said, Allah's Apostle has slaughtered (a cow) on behalf of his wives."