Musnad Ahmad 5:165

Hassan ibn Musa narrated to us, Hammad ibn Salamah narrated to us, from ‘Ata’ ibn al-Sa’ib, from Zadhan, from ‘Ali, who said: I heard the Prophet, peace and blessings of Allah be upon him, saying: "Whoever leaves the place of a single hair of ritual impurity (janabah) without water touching it, Allah the Exalted will do such and such to him of the Fire." ‘Ali said: "Because of that, I became hostile toward my hair."