Musnad Ahmad 27:901

Ahmad ibn Abd al-Malik al-Harrani narrated to us, al-Darawardi informed us, from Ubayd Allah ibn Umar, from Nafi, from Ibn Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever combines his Hajj and his Umrah, one circumambulation (tawaf) is sufficient for both of them."