Al-Adab Al-Mufrad, Book 14, Hadith 303 (English) ⓘ

Anas reported that the Prophet, may Allah bless him and grant him peace, was the best of people, the most generous of people and most courageous of people. One night the people of Madina were alarmed by a noise and the people went towards its source. The Prophet, may Allah bless him and grant him peace, met them, having already reached the source of the noise before them and he was saying, "Do not be alarmed. Do not be alarmed." He was riding a horse belonging to Abu Talha without a saddle and a sword was hung around his neck. He said, "I found it (the horse) like a great river" or it was a great river (meaning its speed).

حَدَّثَنَا عَمْرُو بْنُ عَوْنٍ، قَالَ‏:‏ أَخْبَرَنَا حَمَّادٌ، عَنْ ثَابِتٍ، عَنْ أَنَسٍ قَالَ‏:‏ كَانَ النَّبِيُّ صلى الله عليه وسلم أَحْسَنَ النَّاسِ، وَأَجْوَدَ النَّاسِ، وَأَشْجَعَ النَّاسِ، وَلَقَدْ فَزِعَ أَهْلُ الْمَدِينَةِ ذَاتَ لَيْلَةٍ، فَانْطَلَقَ النَّاسُ قِبَلَ الصَّوْتِ، فَاسْتَقْبَلَهُمُ النَّبِيُّ صلى الله عليه وسلم قَدْ سَبَقَ النَّاسَ إِلَى الصَّوْتِ وَهُوَ يَقُولُ‏:‏ لَنْ تُرَاعُوا، لَنْ تُرَاعُوا، وَهُوَ عَلَى فَرَسٍ لأَبِي طَلْحَةَ عُرْيٍ، مَا عَلَيْهِ سَرْجٌ، وَفِي عُنُقِهِ السَّيْفُ، فَقَالَ‏:‏ لَقَدْ وَجَدْتُهُ بَحْرًا، أَوْ إِنَّهُ لَبَحْرٌ‏.‏