Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) commanded us to cover the water (for ablution), to tie the mouths of water skins with rope, and to turn empty vessels upside down. Imam Abu Bakr (may Allah have mercy on him) says that the Prophet (peace and blessings be upon him) called the water from which ablution is to be performed as "wudu." This is of the same kind that I have mentioned in several places in my books, that the Arabs give something the name at the beginning which it will receive at the end of its use, because water is called "wudu" even before it is used for ablution, as eventually it will be used for ablution.