Sahih Bukhari
Good Manners and Form (Al-Adab)
Volume: 008 / Book Number: 073 / Hadith Number: 149
Narrated Abu Huraira:
A bedouin urinated in the mosque, and the people rushed to beat him. Allah's Apostle ordered them to leave him and pour a bucket or a tumbler (full) of water over the place where he has passed urine. The Prophet then said, " You have been sent to make things easy (for the people) and you have not been sent to make things difficult for them."