Maliks Muwatta Book 002, Hadith Number 079.

Section : Wudu of a Person in a State of Major Ritual Impurity (Janaba).

Yahya related to me from Malik from Hisham ibn Urwa from his father that A'isha, the wife of the Prophet, may Allah bless him and grant him peace, used to say, "If you have intercourse with your wife and then wish to go to sleep before doing ghusl, do not sleep until you have done wudu as for prayer."