Musnad Ahmad 1153:1352

Hushaym narrated to us, he said: Khalid informed us, he said: A man from the people of Kufa narrated to us, from al-Aswad ibn Yazid, from Aisha, she said: "When the Prophet, peace and blessings of Allah be upon him, would exit from his place of bathing where he would bathe from janabah (major ritual impurity), he would wash his feet."