Musnad Ahmad 5:780

Abdullah narrated to us, Ishaq bin Isma'il narrated to us, Waki' narrated to us, Isra'il narrated to us, from Abu Ishaq, from Abu Hayyah al-Wadi'i, who said: I saw Ali, may Allah be pleased with him, urinate in the open courtyard (al-Rahbah). Then he called for water and performed ablution. He washed his palms three times, rinsed his mouth, and inhaled water into his nose three times. He washed his face three times, and washed his forearms three times each. He wiped his head and washed his feet three times each. Then he said: "I saw the Messenger of Allah, may Allah bless him and grant him peace, do as you have seen me do."