It is narrated from Sayyiduna Imran bin Husayn (may Allah be pleased with him) that a man had six slaves and he freed them at the time of his death, "so the Messenger of Allah (peace and blessings be upon him) cast lots between them, freed two and kept four in slavery."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15519