Sayyiduna Anas bin Malik (may Allah be pleased with him) said: A Bedouin came to the Prophet (peace and blessings be upon him). He finished what he needed and then stood in a corner of the mosque and urinated. The Companions (may Allah be pleased with them) wanted to stop him, but the Prophet (peace and blessings be upon him) forbade them. Then he (peace and blessings be upon him) had a bucket of water brought and poured it over that urine.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4234