Musnad Ahmad 33:456

Rawh narrated to us, Ibn Jurayj informed us, Ja'far ibn Muhammad narrated to me that he heard his father narrating that he heard Jabir ibn Abdullah narrating about the Hajj of the Prophet, may Allah bless him and grant him peace, he said: "Then he descended from As-Safa, until when his feet reached the bottom of the valley, he ran, until when we ascended the other side, he walked."