Sahih Bukhari Volume 2, Book 26, Hadith Number 727.

Narated By ‘Urwa : Usama was asked in my presence, “How was the speed of (the camel of) Allah’s Apostle while departing from ‘Arafat during the Hajjatul Wada?” Usama replied, “The Prophet proceeded on with a modest pace, and when there was enough space he would (make his camel) go very fast.”