It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that a Bedouin entered the mosque while the Prophet (peace and blessings be upon him) was seated. He prayed two rak'ahs and then said: "O Allah, have mercy on me and on Muhammad (peace and blessings be upon him), and do not have mercy on anyone besides us." The Prophet (peace and blessings be upon him) said: "You have restricted something vast." Shortly afterwards he urinated in the mosque, and the people rushed towards him. He (peace and blessings be upon him) forbade them and said: "Pour a bucket of water over it. You have been sent to make things easy, not to make them difficult."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4240