Abdur Rahman bin Sabit narrated from Sayyiduna Abu Umamah (may Allah be pleased with him), or perhaps from the brother of Sayyiduna Abu Umamah (may Allah be pleased with him): Once the Noble Prophet (peace and blessings be upon him) saw some people (performing ablution), and on the heel of one of them, an area the size of a dirham, or perhaps the size of a fingernail, had not been touched by water. So the Noble Prophet (peace and blessings be upon him) began to say: "Woe to the heels from the Fire." (The narrator states:) "A person should examine this matter; if he sees a place where water has not reached, then he should perform ablution again."