Musannaf Ibn Abi Shayba 13:745

Abu Bakr narrated to us, he said: Abbad bin al-Awwam narrated to us, from Sa'id, from Qatadah, from Abu al-Malih, that a man emancipated a third of his slave. So it was raised to the Prophet, peace and blessings of Allah be upon him, and he said: "He is free; he has no partner."