It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that one of the noble wives of the Prophet (peace and blessings be upon him) stood up and performed ghusl of janabah from a tub of water. Then the Messenger of Allah (peace and blessings be upon him) stood up to perform ghusl from the leftover water, so she informed him that she had already performed ghusl from that tub before him. The Prophet (peace and blessings be upon him) said: "Indeed, water does not become impure by janabah."