Maliks Muwatta Book 2, Hadith Number 80.
Section : Wudu of a Person in a State of Major Ritual Impurity (Janaba).
Yahya related to me from Malik from Nafi that Abdullah ibn Umar, if he wished to sleep or eat while junub, would wash his face, and his arms to the elbows, and wipe his head. Then he would eat or sleep.