Purification (Kitab Al-Taharah)

Dawud :: Book 1 : Hadith 175

Narrated Some Companions of the Prophet:

The Prophet (peace_be_upon_him) saw a person offering prayer, and on the back of his foot a small part equal to the space of a dirham remained unwashed; the water did not reach it. The Prophet (peace_be_upon_him) commanded him to repeat the ablution and prayer.