Sahih Bukhari Volume 3, Book 44, Hadith Number 681.

Narated By Ibn ‘Umar : The Prophet said, “Whoever manumits his share o a jointly possessed slave, it is imperative on him to manumit the slave completely if he has sufficient money to pay the rest of its price which is to be estimated justly. He should pay his partners their shares and release him (the freed one).