Sahih Bukhari Volume 4, Book 52, Hadith Number 156.

Narated By Anas : The ‘Prophet was the best and the bravest amongst the people. Once the people of Medina got terrified at night, so they went in the direction of the noise (that terrified them). The Prophet met them (on his way back) after he had found out the truth. He was riding an unsaddled horse belonging to Abu Talha and a sword was hanging by his neck, and he was saying, “Don’t be afraid! Don’t be afraid!” He further said, “I found it (i.e. the horse) very fast,” or said, “This horse is very fast.” (Qastala-ni)