Sunan Abi Dawud, Hadith 97 ⓘ
‘Abd Allah b. ‘Amr reported : The Messenger of Allah saw some people (performing ablution) while their heels were dry. He then said : Woe to the heels because of Hell. Perform the ablution in full.
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنْ سُفْيَانَ، حَدَّثَنَا مَنْصُورٌ، عَنْ هِلاَلِ بْنِ يِسَافٍ، عَنْ أَبِي يَحْيَى، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم رَأَى قَوْمًا وَأَعْقَابُهُمْ تَلُوحُ فَقَالَ " وَيْلٌ لِلأَعْقَابِ مِنَ النَّارِ أَسْبِغُوا الْوُضُوءَ " .
also referenced under: Hadith 97 (DarusSalam) & Book 1, Hadith 97 (USC-MSA)