Musnad Ahmad 32:766

Ibn Numayr narrated to us, Yahya narrated to us, from Anas bin Malik, that a Bedouin came to the Messenger of Allah, may Allah bless him and grant him peace, and fulfilled his need, then stood at the side of the mosque. He urinated, so some of the people shouted. The Messenger of Allah, may Allah bless him and grant him peace, restrained them, then ordered a bucket of water, and it was poured over his urine.