Explanation

One of the Prophet's wives took a ritual bath with water placed in a large bowl. Then, the Prophet (may Allah's peace and blessings be upon him) went to make ablution or take a ritual bath with the water left over from his wife's bathing. She told him that she was in a state of Janābah when she used that water, so he instructed her that water is not affected by that, and that it retains its characteristics of being pure in itself and purifying of what is washed with it.