Sahih Bukhari
Manumission of Slaves
Volume: 003 / Book Number: 046 / Hadith Number: 729
Narrated Ibn 'Umar:
The Prophet said, "If one manumits his share of a common slave (Abd), and he has money sufficient to free the remaining portion of the price of the slave (justly estimated), then he should free the slave completely by paying the rest of his price; otherwise the slave is freed partly. "