Sunan Ibn Majah, Chapter: The Chapters on Manumission (of Slaves)

that the Messenger of Allah (saw) said: "Whoever frees his share of a slave, the price of the slave should be fairly evaluated, and he (the partner who initiated this process) should free him (in full, by giving the rest of his price to the other co-owners), if he has enough wealth to do so. Otherwise, he will have freed whatever he freed." Sahih