Narrated Anas (rad):

The Prophet (ﷺ) saw a man on whose foot appeared a portion like the size of a nail which was not touched by water. He then said, “Go back and perform your Wudu properly.” [Reported by Abu Da’ud and An-Nasa’i].

وَعَنْ أَنَسٍ ‏- رضى الله عنه ‏- قَالَ: { رَأَى اَلنَّبِيُّ ‏- صلى الله عليه وسلم ‏-رَجُلًا, وَفِي قَدَمِهِ مِثْلُ اَلظُّفْرِ لَمْ يُصِبْهُ اَلْمَاءُ.‏ فَقَالَ:

اِرْجِعْ فَأَحْسِنْ وُضُوءَكَ

} أَخْرَجَهُ أَبُو دَاوُدَ, وَالنَّسَائِيّ ُ [1]‏ .‏