From Sahih Muslim (Hadith 660):
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: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
Reference: Muslim 660