A person came to the Messenger of Allah ﷺ. He performed ablution and left a small part equal to the space of a nail upon his foot. The Messenger of Allah ﷺ said to him : Go back and perform ablution well. Abu Dawud said: This tradition is not known through Jarir b. Hazim. It was transmitted only by Ibn Wahab. Another version adds the wording : “ Go back and perform the ablution well.”  

أَنَّ رَجُلاً جَاءَ إِلَى النَّبِيِّ ﷺ وَقَدْ تَوَضَّأَ وَتَرَكَ عَلَى قَدَمَيْهِ مِثْلَ مَوْضِعِ الظُّفْرِ فَقَالَ لَهُ رَسُولُ اللَّهِ ﷺ ارْجِعْ فَأَحْسِنْ وُضُوءَكَ  

Hasan narrated from the Prophet ﷺ a tradition conveying the same meaning as that of Qatadah.  

عَنِ النَّبِيِّ ﷺ بِمَعْنَى قَتَادَةَ  

The Prophet ﷺ saw a person offering prayer, and on the back of his foot a small part equal to the space of a dirham remained unwashed; the water did not reach it. The Prophet ﷺ commanded him to repeat the ablution and prayer.  

عَنْ بَعْضِ أَصْحَابِ النَّبِيِّ أَنَّ النَّبِيَّ ﷺ رَأَى رَجُلاً يُصَلِّي وَفِي ظَهْرِ قَدَمِهِ لُمْعَةٌ قَدْرُ الدِّرْهَمِ لَمْ يُصِبْهَا الْمَاءُ فَأَمَرَهُ النَّبِيُّ ﷺ أَنْ يُعِيدَ الْوُضُوءَ وَالصَّلاَةَ