Sunan Abi Dawud 20679
In-book no 175حَدَّثَنَا حَيْوَةُ بْنُ شُرَيْحٍ، حَدَّثَنَا بَقِيَّةُ، عَنْ بَحِيرٍ، - هُوَ ابْنُ سَعْدٍ - عَنْ خَالِدٍ، عَنْ بَعْضِ، أَصْحَابِ النَّبِيِّ أَنَّ النَّبِيَّ صلى الله عليه وسلم رَأَى رَجُلاً يُصَلِّي وَفِي ظَهْرِ قَدَمِهِ لُمْعَةٌ قَدْرُ الدِّرْهَمِ لَمْ يُصِبْهَا الْمَاءُ فَأَمَرَهُ النَّبِيُّ صلى الله عليه وسلم أَنْ يُعِيدَ الْوُضُوءَ وَالصَّلاَةَ .
Narrated Some Companions of the Prophet: 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.