Musannaf Ibn Abi Shayba 1:456

Yazid ibn Harun narrated to us, he said: Muslim ibn Sa'id informed us, from Abu Ali al-Rahbi, from Ikrimah, from Ibn Abbas, that the Prophet, peace and blessings of Allah be upon him, performed ghusl (ritual bath) due to janabah (major ritual impurity). He saw a spot that the water had not reached, so he took from his hair (jummah) and moistened it with it.