Musnad Ahmad 941:91

Waki' narrated to us, Hisham bin 'Urwah narrated to us, from his father, who said: I was sitting with Usamah, and he was asked about the pace of the Prophet (peace and blessings of Allah be upon him) when he departed from 'Arafah. He said: "He would travel at a gentle pace (*al-'anaq*), and when he found an opening, he would increase his speed (*nassa*)," meaning: faster than the gentle pace.