Sunan Ibn Majah #665 · The Book of Purification and its Sunnah

Sunan Ibn MajahIt was narrated from Anas that
Sunan Ibn Majah · Book 1 · The Book of Purification and its Sunnah
Sunan Ibn Majah · كتاب 1 · كتاب الطهارة وسننها
A man came to the Prophet; he had performed ablution and has missed a spot the size of a fingernail where water had not reached. The Prophet said to him: 'Go back and perform ablution properly
حَدَّثَنَا حَرْمَلَةُ بْنُ يَحْيَى، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ وَهْبٍ، حَدَّثَنَا جَرِيرُ بْنُ حَازِمٍ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، أَنَّ رَجُلاً، أَتَى النَّبِيَّ ـ صلى الله عليه وسلم ـ وَقَدْ تَوَضَّأَ وَتَرَكَ مَوْضِعَ الظُّفْرِ لَمْ يُصِبْهُ الْمَاءُ فَقَالَ لَهُ النَّبِيُّ ـ صلى الله عليه وسلم ـ ‏
"‏ ارْجِعْ فَأَحْسِنْ وُضُوءَكَ ‏"‏ ‏.‏
Reference : Sunan Ibn Majah 665In-book reference : Book 1, Hadith 399