Al-Hakam, or Abu al-Hakam al-Thaqafi, (may Allah be pleased with him) said: "I saw the Messenger of Allah (peace and blessings be upon him) urinate; then he called for water, performed ablution and sprinkled it over his private part."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3171