Musnad Ahmad 25:382

Ali ibn Asim narrated to us, from al-Jurayri, from Abu al-Tufayl, and Abdullah ibn Uthman ibn Khuthaym, from Abu al-Tufayl, both of them from Ibn Abbas, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) performed *raml* (brisk walking) for three circuits around the House. When he reached the Yemeni Corner, he walked until he came to the Stone (the Black Stone), then he would perform *raml*, and he walked for four circuits." Ibn Abbas said: "And it was a Sunnah."