Sayyiduna Jubayr bin Mut'im (may Allah be pleased with him) says: The ritual bath for janabah (major impurity) was mentioned in the presence of the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "As for me, I pour water over my head three times."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 840