Musnad Ahmad 22:11

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Abdullah ibn Abi Najih narrated to me, from 'Ata' ibn Abi Rabah, and from Mujahid ibn Jabr, from Abdullah ibn Abbas: My brother, al-Fadl ibn Abbas, narrated to me—and he was with him when he entered it—that the Messenger of Allah, peace and blessings of Allah be upon him, did not pray in the Kaaba. However, when he entered it, he fell prostrate between the two pillars, then he sat supplicating.