Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever sells a slave who has property, the property belongs to the seller, unless the buyer stipulates (otherwise)."
This is a good mursal (mursal hasan).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10770