Musnad Abu Ya'la al-Mawsili 110:268

Zuhayr narrated to us, Yazid ibn Harun narrated to us, Hammam ibn Yahya informed us, 'Ata' narrated to us, from Ibn 'Abbas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) entered the Ka'bah, and there were six pillars in it. He stood at every pillar, but he did not pray.