Hadith 1260
'Abdullah bin Umar (may Allah be pleased with them both) says: I heard the Messenger of Allah (peace and blessings of Allah be upon him) say during a sermon: "Whoever makes a contract of manumission with his slave for one hundred uqiyyah (twelve hundred dirhams), and the slave pays all except ten uqiyyah, then is unable to pay the remainder, he remains a slave."
© Imam Tirmidhi says:
1- This hadith is hasan ghareeb.
2- Hajjaj bin Arta'ah has also narrated a similar hadith from Amr bin Shu'aib.
3- Most of the companions and other scholars act upon this, that as long as any amount of the contract remains unpaid by the slave, he remains a slave.