Sahih al-Bukhari 6033
Narrated Anas:
The Prophet (ﷺ) was the best among the people (both in shape and 
     character) and was the most generous of them, and was the bravest of 
     them. Once, during the night, the people of Medina got afraid (of a 
     sound). So the people went towards that sound, but the Prophet (ﷺ) having 
     gone to that sound before them, met them while he was saying, "Don't 
     be afraid, don't be afraid." (At that time) he was riding a horse 
     belonging to Abu Talha and it was naked without a saddle, and he was 
     carrying a sword slung at his neck. The Prophet (ﷺ) said, "I found it (the
     horse) like a sea, or, it is the sea indeed."
حَدَّثَنَا عَمْرُو بْنُ عَوْنٍ، حَدَّثَنَا حَمَّادٌ ـ هُوَ ابْنُ زَيْدٍ ـ 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 وَهْوَ يَقُولُ ‏"‏ لَنْ تُرَاعُوا، لَنْ تُرَاعُوا ‏"‏‏.‏ وَهْوَ عَلَى فَرَسٍ لأَبِي طَلْحَةَ عُرْىٍ مَا عَلَيْهِ سَرْجٌ، فِي عُنُقِهِ سَيْفٌ فَقَالَ ‏"‏ لَقَدْ وَجَدْتُهُ بَحْرًا ‏"‏‏.‏ أَوْ ‏"‏ إِنَّهُ لَبَحْرٌ ‏"‏‏.‏