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."
Hadith Referenceسنن الدارقطني / كتاب الطهارة / 380
Hadith Gradingمحدثین:إسناده ضعيف
Hadith Takhrij«إسناده ضعيف ، وأخرجه البيهقي فى((سننه الكبير)) برقم: 399، والدارقطني فى ((سننه)) برقم: 380، وابن أبى شيبة فى ((مصنفه)) برقم: 273، والطبراني فى((الكبير)) برقم: 8109» «قال ابن عبدالبر: روي من حديث أبي أمامة وفيه ضعف ، التمهيد لما في الموطأ من المعاني والأسانيد: (24 / 247)»