Musnad Ahmad 790:118

Yahya ibn Ishaq narrated to us, Hammad ibn Zayd informed us, from Yahya ibn Atiq, from Muhammad ibn Sirin, from Imran ibn Husayn, that a man emancipated six slaves of his. The Messenger of Allah, peace and blessings of Allah be upon him, drew lots among them, so he emancipated two and kept four in slavery. Muhammad ibn Sirin said: If it had not reached me that the Messenger of Allah, peace and blessings of Allah be upon him, said it, I would have made it my own opinion.