Sahih Muslim 284b
Sahih Muslim · Book 2: The Book of Purification · The obligation to wash away urine and other impurities if they result in the Masjid, and the ground may be purified with water with no need to scrub it
Anas b. Malik narrated that a desert Arab (Bedouin) stood in a corner of the mosque and urinated there. The people (the Companions of the Prophet who were present there) shouted, but the Messenger of Allah (ﷺ) said:
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى ، حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ الْقَطَّانُ ، عَنْ يَحْيَى بْنِ سَعِيدٍ الأَنْصَارِيِّ ، ح وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى ، وَقُتَيْبَةُ بْنُ سَعِيدٍ ، جَمِيعًا عَنِ الدَّرَاوَرْدِيِّ ، - قَالَ يَحْيَى بْنُ يَحْيَى أَخْبَرَنَا عَبْدُ الْعَزِيزِ بْنُ مُحَمَّدٍ الْمَدَنِيُّ، - عَنْ يَحْيَى بْنِ سَعِيدٍ ، أَنَّهُ سَمِعَ أَنَسَ بْنَ مَالِكٍ ، يَذْكُرُ أَنَّ أَعْرَابِيًّا، قَامَ إِلَى نَاحِيَةٍ فِي الْمَسْجِدِ فَبَالَ فِيهَا فَصَاحَ بِهِ النَّاسُ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " دَعُوهُ " . فَلَمَّا فَرَغَ أَمَرَ رَسُولُ اللَّهِ صلى الله عليه وسلم بِذَنُوبٍ فَصُبَّ عَلَى بَوْلِهِ .
Leave him alone. When he had finished, the Messenger of Allah (ﷺ) ordered that a bucket (of water) should be brought and poured over it.