Sayyiduna Imran bin Husayn (may Allah be pleased with him) says that a man freed six slaves at the time of his death, and he had no wealth besides them. When he (peace and blessings be upon him) came to know of it, he (peace and blessings be upon him) drew lots between them; he (peace and blessings be upon him) freed two and kept four in slavery.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21395