(67) باب تَفْرِيقِ الْوُضُوءِ
Narrated Some Companions of the Prophet:
The Prophet (ﷺ) 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 (ﷺ) commanded him to repeat the ablution and prayer.
Reference: Sunan Abi Dawud 175
In-book reference: Book 1, Hadith 175
English translation: Book 1, Hadith 175