It is narrated from Sayyiduna Ali (may Allah be pleased with him) that I heard the Prophet (peace and blessings of Allah be upon him) say: Whoever, while performing ghusl in the state of major impurity, leaves even an area equal to a single hair where water does not reach, Allah the Exalted will deal with him in such and such a manner in Hell. From that very moment, I developed enmity with my hair.