Sahih Muslim | Book 2 | Hadith Number 557

Narrated by Anas
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 (may peace be upon him) 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.