Sahih Bukhari Volume 4, Book 52, Hadith Number 119.

Narated By Anas bin Malik : Once the people of Medina were frightened, so the Prophet rode a horse belonging to Abu Talha and it ran slowly, or was of narrow paces. When he returned, he said, “I found your (i.e. Abu Talha’s) horse very fast. After that the horse could not be surpassed in running.