‘Umair, the freed slave of Abdullah ibn Mas‘ud (may Allah be pleased with him), says that Ibn Mas‘ud (may Allah be pleased with them both) said to him: Umair! I have set you free gladly. I heard the Messenger of Allah (peace and blessings of Allah be upon him) say:“Whoever frees a slave and does not mention his property, then the property belongs to the slave.”Tell me, what property do you have?

A similar hadith is narrated through this chain as well.