Sayyiduna Jubayr bin Mut'im (may Allah be pleased with him) narrated: We discussed the ritual bath (ghusl) for major impurity (janabah) in the presence of the Prophet (peace and blessings be upon him), and a man among us said: How should we do it? The Prophet (peace and blessings be upon him) said: "As for me, I take a palmful of water and pour it over my head, then after that I pour it over the rest of my body."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1470