Sahih al-Bukhari 219
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · The Prophet (saw) and the people left the bedouin undisturbed till he finished urinating in the mosque
Narrated Anas bin Malik:
حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ ، قَالَ حَدَّثَنَا هَمَّامٌ ، أَخْبَرَنَا إِسْحَاقُ ، عَنْ أَنَسِ بْنِ مَالِكٍ ، أَنَّ النَّبِيَّ صلى الله عليه وسلم رَأَى أَعْرَابِيًّا يَبُولُ فِي الْمَسْجِدِ فَقَالَ " دَعُوهُ ". حَتَّى إِذَا فَرَغَ دَعَا بِمَاءٍ فَصَبَّهُ عَلَيْهِ.
The Prophet (ﷺ) saw a Bedouin making water in the mosque and told the people not to disturb him. When he finished, the Prophet (ﷺ) asked for some water and poured it over (the urine).