The people were struck with alarm, so the Messenger of Allah ﷺ mounted a slow horse belonging to Abu Talha and rode out alone at full speed. The people then mounted and galloped after him. He said, "Do not be afraid. Indeed, he is a sea." After that day, the horse was never outrun.
فزع الناس، فركب رسول الله ﷺ فرسا لأبي طلحة بطيئا، ثم خرج يركض وحده، فركب الناس يركضون خلفه فقال: لم تراعوا إنه لبحر فما سبق بعد ذلك اليوم.
Bukhari narrated it in jihad (2969), from Fadl bin Sahl, who said, Husayn bin Muhammad narrated to us, who said, Jareer bin Hazim narrated to us, from Muhammad, from Anas bin Malik, and he related it. Muslim also narrated it through another route from Anas in virtues (48:2307).