Musannaf Ibn Abi Shayba 1:1067

Aswad ibn Amir narrated to us, he said: Hammad ibn Salamah narrated to us, from Ata’ ibn al-Sa’ib, from Zadhan, from Ali, from the Prophet (peace and blessings of Allah be upon him), who said: "Whoever leaves a place of a hair on his body from janabah (major ritual impurity) without washing it, such and such will be done to him of the Fire." Ali said: "From then on, I became hostile [to my hair]." He said: "And he used to shear his hair."