Musnad Ahmad 1153:932

Muhammad ibn Ja‘far narrated to us, he said: Shu‘bah narrated to us, from al-Hakam, he said: I heard Ibrahim narrating from al-Aswad, from ‘Aishah, that she said: "When the Messenger of Allah, peace and blessings of Allah be upon him, was in a state of major ritual impurity (janabah) and wished to sleep or eat, he would perform ablution (wudu)."