[Machine] I was one of seven with the Messenger of Allah ﷺ . He commanded us to gather a dirham for each of us, so we bought a sacrificial animal for seven dirhams. We said, "O Messenger of Allah, it is too expensive for us!" The Prophet ﷺ said, "Indeed, the best sacrifice is the most expensive, fattest one." So a man took hold of a leg, another took hold of a leg, and similarly a man took hold of a hand, another of a hand, two others took hold of a horn each. The seventh one slaughtered it and we all said the takbeer.  

كُنْتُ سَابِعَ سَبْعَةٍ مَعَ رَسُولِ اللهِ ﷺ قَالَ فَأَمَرَنَا نَجْمَعُ لِكُلِّ رَجُلٍ مِنَّا دِرْهَمًا فَاشْتَرَيْنَا أُضْحِيَّةً بِسَبْعَةِ الدَّرَاهِمِ فَقُلْنَا يَا رَسُولَ اللهِ لَقَدْ أَغْلَيْنَا بِهَا؟ فَقَالَ النَّبِيُّ ﷺ إِنَّ أَفْضَلَ الضَّحَايَا أَغْلَاهَا وَأَسْمَنُهَا وَأَمَرَ رَسُولُ اللهِ ﷺ فَأَخَذَ رَجُلٌ بِرِجْلٍ وَرَجُلٌ بِرِجْلٍ وَرَجُلٌ بِيَدٍ وَرَجُلٌ بِيَدٍ وَرَجُلٌ بِقَرْنٍ وَرَجُلٌ بِقَرْنٍ وَذَبَحَهَا السَّابِعُ وَكَبَّرْنَا عَلَيْهَا جَمِيعًا  

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. (Using translation from Abū Dāʾūd 175)   

عَنْ بَعْضِ أَصْحَابِ النَّبِيِّ ﷺ أَنَّ رَسُولَ اللهِ ﷺ رَأَى رَجُلًايُصَلِّي وَفِي ظَهْرِ قَدَمِهِ لُمْعَةٌ قَدْرُ الدِّرْهَمِ لَمْ يُصِبْهَا الْمَاءُ فَأَمَرَهُ رَسُولُ اللهِ ﷺ أَنْ يُعِيدَ الْوُضُوءَ