Sahih Bukhari
Fighting for the Cause of Allah (Jihaad)
Volume: 004 / Book Number: 052 / Hadith Number: 119
Narrated 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..'