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 187

Narrated Abu Juhaifa:

Allah's Messenger (ﷺ) came to us at noon and water for ablution was brought to him. After he had performed ablution, the remaining water was taken by the people and they started smearing their bodies with it (as a blessed thing). The Prophet (ﷺ) offered two rak`at of the Zuhr prayer and then two rak`at of the `Asr prayer while a short spear (or stick) was there (as a Sutra) in front of him.

حَدَّثَنَا آدَمُ، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ حَدَّثَنَا الْحَكَمُ، قَالَ سَمِعْتُ أَبَا جُحَيْفَةَ، يَقُولُ خَرَجَ عَلَيْنَا رَسُولُ اللَّهِ صلى الله عليه وسلم بِالْهَاجِرَةِ، فَأُتِيَ بِوَضُوءٍ فَتَوَضَّأَ، فَجَعَلَ النَّاسُ يَأْخُذُونَ مِنْ فَضْلِ وَضُوئِهِ فَيَتَمَسَّحُونَ بِهِ، فَصَلَّى النَّبِيُّ صلى الله عليه وسلم الظُّهْرَ رَكْعَتَيْنِ وَالْعَصْرَ رَكْعَتَيْنِ، وَبَيْنَ يَدَيْهِ عَنَزَةٌ‏.‏
Reference : Sahih al-Bukhari 187
In-book reference : Book 4, Hadith 53
USC-MSA web (English) reference : Vol. 1, Book 4, Hadith 187
  (deprecated numbering scheme)