Musnad Abu Ya'la al-Mawsili 246:27

Ishaq narrated to us, al-Nadr ibn Shumayl narrated to us, Shu'bah narrated to us, from Abu Ishaq, who said: I heard Sulayman ibn Surad say: I heard Jubayr ibn Mut'im say: The washing from sexual impurity (janabah) was mentioned in the presence of the Messenger of Allah, may Allah bless him and grant him peace. The Messenger of Allah, may Allah bless him and grant him peace, said: "As for me, I pour three [handfuls] over my head."