Abu Dawud Book 1, Hadith Number 380.

Chapter : The earth smeared with urine.

Narated By Abu Hurairah : A bedouin entered the mosque while the Apostle of Allah (PBUH) was sitting. He offered two rak’ahs of prayer, according to the version of Ibn ‘Abdah. He then said: O Allah, have mercy on me and on Muhammad and do not have mercy on anyone along with us. The Prophet (PBUH) said: You have narrowed down (a thing) that was broader. After a short while he passed water in a corner of the mosque. The people rushed towards him. The Prophet (PBUH) prevented them and said: You have been sent to facilitate and not create difficulties. Pour a bucket of water upon it.