It is narrated from Hazrat Aisha that once the Prophet (peace be upon him) went to relieve himself, and Hazrat Umar stood behind him with a bowl of water. After finishing, the Prophet (peace be upon him) asked, "Umar! What is this?" He replied, "O Messenger of Allah! This is water for your ablution." The Prophet (peace be upon him) said, "I have not been commanded that I must perform ablution every time I urinate, because if I start doing so, this act will become Sunnah."