Musannaf Ibn Abi Shayba 35:274

Waki’ narrated to us, from Sufyan, from Salamah ibn Kuhayl, from the one who heard Jabir ibn Abdullah saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever sells a slave who has wealth, then his wealth belongs to the seller, unless the buyer stipulates [otherwise]." The Messenger of Allah (peace and blessings of Allah be upon him) judged accordingly.