The Prophet ﷺ remained behind us on a journey. He joined us while we were performing ablution for the ʿAsr prayer which was overdue and we were just passing wet hands over our feet (not washing them thoroughly) so he addressed us in a loud voice saying twice , "Save your heels from the fire."  

تَخَلَّفَ النَّبِيُّ ﷺ عَنَّا فِي سَفْرَةٍ سَافَرْنَاهَا فَأَدْرَكَنَا وَقَدْ أَرْهَقْنَا الْعَصْرَ فَجَعَلْنَا نَتَوَضَّأُ وَنَمْسَحُ عَلَى أَرْجُلِنَا فَنَادَى بِأَعْلَى صَوْتِهِ وَيْلٌ لِلأَعْقَابِ مِنَ النَّارِ مَرَّتَيْنِ أَوْ ثَلاَثًا