Musannaf Ibn Abi Shayba 3:6079

'Abbad ibn al-'Awwam narrated to us, from Husayn ibn Zayd, who said: I saw Ibn 'Umar enter the House (the Ka'bah), and he prayed two rak'ahs. Then he moved and prayed two rak'ahs from the side adjacent to the corner (al-rukn). Then I went out and left him standing, supplicating and saying the takbir.