Anas reported:A person came to the Messenger of Allah (ﷺ). He performed ablution and left a small part equal to the space of a nail upon his foot. The Messenger of Allah (ﷺ) said to him : Go back and perform ablution well. Abu Dawud said: This tradition is not known through Jarir b. Hazim. It was transmitted only by Ibn Wahab. Another version adds the wording : “ Go back and perform the ablution well.”

English translation · Sunan Abu Dawud