Sayyiduna Abdullah bin Umar (may Allah be pleased with him) narrates that the Noble Prophet (peace and blessings be upon him) said: "Whoever sells a slave who possesses property, then the property belongs to the seller, unless the buyer stipulates a condition."
Hadith Referenceالمنتقى ابن الجارود / كتاب البيوع والتجارات / 629