Abu al-Malih (may Allah have mercy on him) narrates from his father that a man freed his share of a slave. This was mentioned to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Allah has no partner." Ibn Kathir (may Allah have mercy on him) added some words: that the Prophet (peace and blessings be upon him) validated his freeing (of the slave).
The Shaykh (may Allah have mercy on him) said: It is possible that this refers to one who freed his share of a slave jointly owned between him and someone else, and another meaning is also possible.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21316