Musnad Abu Ya'la al-Mawsili 150:201

Ahmad ibn Zayd narrated to us, Hammad ibn Khalid narrated to us, from Aflah ibn Humayd, from al-Qasim ibn Muhammad, from Aisha, the Mother of the Believers, who said: The Messenger of Allah (may Allah bless him and grant him peace) had intercourse with some of his wives, then he slept until he reached the morning while he was in a state of major ritual impurity (junub). He then performed ghusl and fasted his day.