Musnad Ahmad 1153:2090

'Uthman narrated to us, Yunus narrated to us, from al-Zuhri, who said: I found in one place from 'Urwah, and another place from 'Amrah—both of them were stated by 'Uthman—from 'Aishah: "That the Messenger of Allah (ﷺ) slaughtered a cow on behalf of his wives during the Farewell Pilgrimage."