(30) باب وُجُوبِ غَسْلِ الْبَوْلِ وَغَيْرِهِ مِنَ النَّجَاسَاتِ إِذَا حَصُلَتْ فِي الْمَسْجِدِ وَأَنَّ الأَرْضَ تَطْهُرُ بِالْمَاءِ مِنْ غَيْرِ حَاجَةٍ إِلَى حَفْرِهَا
Anas reported:
A Bedouin urinated in the mosque. Some of the persons stood up (to reprimand him or to check him from doing so), but the Messenger of Allah (ﷺ) said: Leave him alone; don't interrupt him. He (the narrator) said: And when he had finished, he called for a bucket of water and poured it over.
Reference: Sahih Muslim 284a
In-book reference: Book 2, Hadith 125
USC-MSA web (English) reference(deprecated numbering scheme): Book 2, Hadith 557