The obligation of washing the feet completely
وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا جَرِيرٌ، ح وَحَدَّثَنَا إِسْحَاقُ، أَخْبَرَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ هِلاَلِ بْنِ يِسَافٍ، عَنْ أَبِي يَحْيَى، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، قَالَ رَجَعْنَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم مِنْ مَكَّةَ إِلَى الْمَدِينَةِ حَتَّى إِذَا كُنَّا بِمَاءٍ بِالطَّرِيقِ تَعَجَّلَ قَوْمٌ عِنْدَ الْعَصْرِ فَتَوَضَّئُوا وَهُمْ عِجَالٌ فَانْتَهَيْنَا إِلَيْهِمْ وَأَعْقَابُهُمْ تَلُوحُ لَمْ يَمَسَّهَا الْمَاءُ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " وَيْلٌ لِلأَعْقَابِ مِنَ النَّارِ أَسْبِغُوا الْوُضُوءَ " .
'Abdullah b. 'Amr reported: We returned from Mecca to Medina with the Messenger of Allah (ﷺ), and when we came to some water on the way, some of the people were in a hurry at the time of the afternoon prayer and performed ablution hurriedly; and when we reached them, their heels were dry, no water had touched them. The Prophet (ﷺ) said: Woe to (dry) heels, because of Hell-fire. Make your ablution thorough.