عَنْ عَبْدِ اللَّهِ بْنِ عَمْرِو بْنِ الْعَاصِ رَضِيَ اللَّهُ عَنْهُ قَالَ: رَأَى رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَوْمًا يَتَوَضَّأُونَ وَأَعْقَابُهُمْ تَلُوحُ فَقَالَ: ((وَيْلٌ لِلْأَعْقَابِ مِنَ النَّارِ، أَسْبِغُوا الْوُضُوءَ))
It is narrated from Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) saw some people who had performed ablution, but the dryness of their heels was clearly visible, so he (peace and blessings be upon him) said: "Woe to the heels from the Fire! Perform ablution thoroughly."