Sahih Bukhari | Volume 3 | Hadith Number 698

Narrated by 'Abdullah bin 'Umar
Allah's Apostle said, "Whoever frees his share of a common slave and he has sufficient money to free him completely, should let its price be estimated by a just man and give his partners the price of their shares and manumit the slave; otherwise (i.e. if he has not sufficient money) he manumits the slave partially."