Language:
كتاب الوضوء
4
Ablutions (Wudu')
(3)
Chapter: Chapter. The Superiority Of Ablution. And Al-ghurr-ul-muhajjalun (the Parts Of The Body Of The Muslims Washed In Ablution Will Shine On The Day Of Ressurrection And The Angels Will Call Them By That Name) From The Traces Of Ablution
(3)
باب فَضْلِ الْوُضُوءِ، وَالْغُرُّ الْمُحَجَّلُونَ مِنْ آثَارِ الْوُضُوءِ

Narrated Nu`am Al-Mujmir:

Once I went up the roof of the mosque, along with Abu Huraira. He perform ablution and said, "I heard the Prophet (ﷺ) saying, "On the Day of Resurrection, my followers will be called "Al-Ghurr-ul- Muhajjalun" from the trace of ablution and whoever can increase the area of his radiance should do so (i.e. by performing ablution regularly).' "

حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ خَالِدٍ، عَنْ سَعِيدِ بْنِ أَبِي هِلاَلٍ، عَنْ نُعَيْمٍ الْمُجْمِرِ، قَالَ رَقِيتُ مَعَ أَبِي هُرَيْرَةَ عَلَى ظَهْرِ الْمَسْجِدِ، فَتَوَضَّأَ فَقَالَ إِنِّي سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ ‏ "‏ إِنَّ أُمَّتِي يُدْعَوْنَ يَوْمَ الْقِيَامَةِ غُرًّا مُحَجَّلِينَ مِنْ آثَارِ الْوُضُوءِ، فَمَنِ اسْتَطَاعَ مِنْكُمْ أَنْ يُطِيلَ غُرَّتَهُ فَلْيَفْعَلْ ‏"‏‏.‏
Reference : Sahih al-Bukhari 136
In-book reference : Book 4, Hadith 2
USC-MSA web (English) reference : Vol. 1, Book 4, Hadith 138
  (deprecated numbering scheme)