Sunan Ibn Majah, Chapter: The Chapters of Purification and its Sunnah

said: "A Bedouin entered the mosque when the Messenger of Allah (saw) was sitting there, and (the man) said: 'O Allah, forgive me and Muhammad (SAW), and do not forgive anyone else with us.' The Messenger of Allah (saw) smiled and said: 'You have placed restrictions on something that is vast.' Then the Bedouin turned away, went to a corner of the mosque, spread his legs and began to urinate. After he had a better understanding, the Bedouin said: 'He got up and came to me, and may my father and mother be ransomed for him, he did not rebuke me nor revile me. He said: "This mosque is not for urinating in. Rather it is built for the remembrance of Allah and prayer.'" Then he called for a large vessel of water and poured it over the place where he had urinated." (Hasan)