Language:
كتاب المناقب
61  
Virtues and Merits of the Prophet (pbuh) and his Companions
(25)
Chapter: The signs of Prophethood in Islam
(25)
باب عَلاَمَاتِ النُّبُوَّةِ فِي الإِسْلاَمِ
Sahih al-Bukhari 3572

Narrated Anas:

A bowl of water was brought to the Prophet (ﷺ) while he was at Az-Zawra. He placed his hand in it and the water started flowing among his fingers. All the people performed ablution (with that water). Qatada asked Anas, "How many people were you?" Anas replied, "Three hundred or nearly three hundred."

حَدَّثَنِي مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، عَنْ سَعِيدٍ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ أُتِيَ النَّبِيُّ صلى الله عليه وسلم بِإِنَاءٍ وَهْوَ بِالزَّوْرَاءِ، فَوَضَعَ يَدَهُ فِي الإِنَاءِ، فَجَعَلَ الْمَاءُ يَنْبُعُ مِنْ بَيْنِ أَصَابِعِهِ، فَتَوَضَّأَ الْقَوْمُ‏.‏ قَالَ قَتَادَةُ قُلْتُ لأَنَسٍ كَمْ كُنْتُمْ قَالَ ثَلاَثَمِائَةٍ، أَوْ زُهَاءَ ثَلاَثِمِائَةٍ‏.‏
Reference : Sahih al-Bukhari 3572
In-book reference : Book 61, Hadith 81
USC-MSA web (English) reference : Vol. 4, Book 56, Hadith 772
  (deprecated numbering scheme)