Musnad Ahmad 33:1055

I read to Abd al-Rahman: Malik, narrated to us Ishaq, informed us Malik, from Ja'far, from his father, from Jabir ibn Abdullah: "That the Messenger of Allah, peace and blessings of Allah be upon him, when he descended from al-Safa, he would walk until his feet reached the bottom of the valley, then he would run (sa'a) until he exited it."