Hadith 11:20
‘Amr b. Shu'aib, on his father’s authority, told that his grandfather reported God's Messenger as saying, “If anyone has agreed to let his slave buy his freedom for a hundred uqiyas and he pays them all but ten (or he said, ten dinars), and he is then unable to complete the amount, he remains a slave.” Tirmidhi, Abu Dawud and Ibn Majah transmitted it.
وَعَنْ عَمْرِو بْنِ شُعَيْبٍ عَنْ أَبِيهِ عَنْ جَدِّهِ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: " مَنْ كَاتَبَ عَبْدَهُ عَلَى مِائَةِ أُوقِيَّةٍ فَأَدَّاهَا إِلَّا عَشْرَ أَوَاقٍ أَوْ قَالَ: عَشْرَةَ دَنَانِيرَ ثُمَّ عَجَزَ فَهُوَ رَقِيقٌ " رَوَاهُ التِّرْمِذِيّ وَأَبُو دَاوُد وَابْن مَاجَه
Original Reference: Mishkat al-Masabih 3401