Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) said: "Whoever frees his share in a slave, the remaining value of the slave shall be assessed from his wealth, it shall be paid to his partner, and the slave shall be set free."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21324