Musannaf Ibn Abi Shayba 13:1810

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Yunus, he said: They claimed that al-Hasan used to say regarding a man who emancipated a portion of his slave at the time of his death: He said: That which was emancipated of him is emancipated, and he is to work to earn his freedom for what remains.