Sahih Bukhari Volume 008, Book 073, Hadith Number 054.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 73. Good Manners and Form (Al-Adab)
Narated By Anas bin Malik : A Bedouin urinated in the mosque and the people ran to (beat) him. Allah's Apostle said, "Do not interrupt his urination (i.e. let him finish)." Then the Prophet asked for a tumbler of water and poured the water over the place of urine.