Sahih Muslim
The Book of Oaths (Kitab Al-Aiman)
Book Number: 015 / Hadith Number: 4102
Ibn 'Umar reported Allah's Messenger (may peace be upon him) as saying: He who gives up his share in a slave, and has enough money to pay the full price of the slave, then full emancipation devolves upon him; but if he has not the money, then he emancipated what he emancipated.