Musnad Ahmad 1153:857

Muhammad ibn Bakr narrated to us, he said: Yunus informed us, he said: Ibn Shihab narrated to me, from the one who narrated to him, from Aisha, she said: "When the Messenger of Allah, may Allah bless him and grant him peace, intended to sleep while he was in a state of major ritual impurity (junub), he would perform his ablution for prayer. And when he intended to eat, he would wash his hands, then eat."