Sayyiduna Ibn 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, a fair value shall be fixed, he shall give it to his partners and the slave shall be free, if he is wealthy; otherwise, as much is free as was freed, and the rest shall remain a slave."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21363