Sahih Bukhari Volume 8, Book 73, Hadith Number 149.

Narated By 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.”