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."
Source: sunnah.com
Other translations
Arabic
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.
sunnah.com