Abu al-Malih (may Allah have mercy on him) said that a man from his people freed one third of his slave. The Prophet (peace and blessings be upon him) was informed, and he (peace and blessings be upon him) said: "He is completely free; Allah has no partner."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21317