It is narrated from Amir al-Mu'minin Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever leaves even a hair's breadth unwashed during the ritual bath of janabah will face a severe punishment of Hell." Sayyiduna Ali (may Allah be pleased with him) said: "Because of this, I became an enemy to my own head," and he used to shave his hair.