Mishkat al-Masabih 29 Excellent Qualities and Description of the Prophet كتاب الفضائل والشمائل 161

وَعَن أنسٍ أَنَّ أَهْلَ الْمَدِينَةِ فَزِعُوا مَرَّةً فَرَكِبَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَرَسًا لِأَبِي طَلْحَةَ بَطِيئًا وَكَانَ يَقْطِفُ فَلَمَّا رَجَعَ قَالَ: «وَجَدْنَا فَرَسَكُمْ هَذَا بَحْرًا» . فَكَانَ بَعْدَ ذَلِكَ لَا يُجَارَى وَفِي رِوَايَةٍ: فَمَا سُبِقَ بَعْدَ ذَلِكَ الْيَوْم. رَوَاهُ البُخَارِيّ

Anas told that, once when the people of Medina had an alarm the Prophet mounted a slow horse belonging to Abu Talha which took short steps. When he returned, he said, “I found this horse of yours could run like a great river.” After that it had none to compete with it. A version says it was never outstripped after that day. Bukhari transmitted it.