Musnad Ahmad 27:816

Waki’ narrated to us, from his father, from ‘Ata’, from Kathir ibn Jumhan, who said: I saw Ibn ‘Umar walking in the valley between al-Safa and al-Marwah, and he was not jogging. So I said to him [about that], and he said: "If I jog, I have seen the Messenger of Allah (peace and blessings of Allah be upon him) jog, and if I walk, I have seen the Messenger of Allah (peace and blessings of Allah be upon him) walk, and I am an old man."