Musnad Ahmad 1153:2136

Yahya ibn Adam narrated to us, he said: Isra'il narrated to us, from Mansur, from Ibrahim, from al-Aswad, from Aisha, she said: "I used to twist the garlands for the sacrificial animals (hady) of the Messenger of Allah, peace and blessings of Allah be upon him, and then he would remain [in the state of Ihram]. She said: And he used to offer sheep as sacrificial animals."