Language:
كتاب الوضوء
4  
Ablutions (Wudu')
(40)
Chapter: The using of the remaining water after ablution
(40)
باب اسْتِعْمَالِ فَضْلِ وَضُوءِ النَّاسِ
Sahih al-Bukhari 189

Narrated Ibn Shihab:

Mahmud bin Ar-Rabi` who was the person on whose face the Prophet (ﷺ) had ejected a mouthful of water from his family's well while he was a boy, and `Urwa (on the authority of Al-Miswar and others) who testified each other, said, "Whenever the Prophet (ﷺ) , performed ablution, his companions were nearly fighting for the remains of the water."

حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ بْنِ سَعْدٍ، قَالَ حَدَّثَنَا أَبِي، عَنْ صَالِحٍ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي مَحْمُودُ بْنُ الرَّبِيعِ، قَالَ وَهُوَ الَّذِي مَجَّ رَسُولُ اللَّهِ صلى الله عليه وسلم فِي وَجْهِهِ وَهْوَ غُلاَمٌ مِنْ بِئْرِهِمْ‏.‏ وَقَالَ عُرْوَةُ عَنِ الْمِسْوَرِ وَغَيْرِهِ يُصَدِّقُ كُلُّ وَاحِدٍ مِنْهُمَا صَاحِبَهُ وَإِذَا تَوَضَّأَ النَّبِيُّ صلى الله عليه وسلم كَادُوا يَقْتَتِلُونَ عَلَى وَضُوئِهِ‏.‏
Reference : Sahih al-Bukhari 189
In-book reference : Book 4, Hadith 55
USC-MSA web (English) reference : Vol. 1, Book 4, Hadith 188
  (deprecated numbering scheme)