حَدَّثَنَا مُسَدَّدٌ ، قَالَ : حَدَّثَنَا أَبُو عَوَانَةَ ، عَنْ أَبِي بِشْرٍ ، عَنْ يُوسُفَ بْنِ مَاهَكَ ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو ، قَالَ : تَخَلَّفَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي سَفَرٍ سَافَرْنَاهُ ، فَأَدْرَكَنَا وَقَدْ أَرْهَقْنَا الصَّلَاةَ صَلَاةَ الْعَصْرِ وَنَحْنُ نَتَوَضَّأُ فَجَعَلْنَا نَمْسَحُ عَلَى أَرْجُلِنَا ، فَنَادَى بِأَعْلَى صَوْتِهِ : وَيْلٌ لِلْأَعْقَابِ مِنَ النَّارِ مَرَّتَيْنِ أَوْ ثَلَاثًا .
In one journey, the Messenger of Allah (peace and blessings of Allah be upon him) was left behind. Then you came near us. So it was time for Asr prayer or it was too late and we were performing ablution. When we started splashing water on our feet, he said in a loud voice that those heels (which remain dry) are damaged by the punishment of fire. He said this twice or thrice.
Sahih Bukhari
Hadeeth No #96