Sunan Ibn Majah Book 1, Hadith 198
"The Messenger of Allah performed ablution and sprinkled his private part."
"The Messenger of Allah said: 'When you perform ablution, sprinkle water.'"
When it was the year of the Conquest (of Makkah), the Messenger of Allah got up to perform a bath and Fatimah screened him. Then he took his garment and wrapped himself in it (such that it became like the towel used to dry oneself).