وَعَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ
عَنْ اَلنَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ -«قَالَ: «اَلْمُكَاتَبُ عَبْدٌ مَا بَقِيَ عَلَيْهِ مِنْ مُكَاتَبَتِهِ دِرْهَمٌ»
“A slave who entered into an agreement to buy his freedom is still a slave as long as a Dirham of the agreed price remains to be paid.” Related by Abu Dawud with a good chain of narrators. The full hadith is related by Ahmad and the three Imams. Al-Hakim graded it to be Sahih.