"A Bedouin entered the Masjid while the Prophet was sitting. He prayed, then when he was finished, he said: 'O Allah! Have mercy upon me and Muhammad, and do not have mercy on anyone along with us.' The Prophet turned, towards him and said: 'You have restricted something that is unrestricted.' It was not long before he was urinating in the Masjid. So the people rushed to him. But Prophet said: 'Pour a bucket of water over it - or - a tumbler of water over it.' Then he said: 'You have been sent to make things easy (for the people); you have not been sent to make things difficult for them.'"
حَدَّثَنَا ابْنُ أَبِي عُمَرَ، وَسَعِيدُ بْنُ عَبْدِ الرَّحْمَنِ الْمَخْزُومِيُّ، قَالاَ حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنِ الزُّهْرِيِّ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ دَخَلَ أَعْرَابِيٌّ الْمَسْجِدَ وَالنَّبِيُّ صلى الله عليه وسلم جَالِسٌ فَصَلَّى فَلَمَّا فَرَغَ قَالَ اللَّهُمَّ ارْحَمْنِي وَمُحَمَّدًا وَلاَ تَرْحَمْ مَعَنَا أَحَدًا . فَالْتَفَتَ إِلَيْهِ النَّبِيُّ صلى الله عليه وسلم فَقَالَ " لَقَدْ تَحَجَّرْتَ وَاسِعًا " . فَلَمْ يَلْبَثْ أَنْ بَالَ فِي الْمَسْجِدِ فَأَسْرَعَ إِلَيْهِ النَّاسُ فَقَالَ النَّبِيُّ صلى الله عليه وسلم " أَهْرِيقُوا عَلَيْهِ سَجْلاً مِنْ مَاءٍ أَوْ دَلْوًا مِنْ مَاءٍ " . ثُمَّ قَالَ " إِنَّمَا بُعِثْتُمْ مُيَسِّرِينَ وَلَمْ تُبْعَثُوا مُعَسِّرِينَ " .
Tirmizi
The Book on Purification • Hadith 147