Sahih al-Bukhari 2492
Narrated Abu Huraira:
The Prophet (ﷺ) said, "Whoever manumits his share of a jointly possessed slave, it is imperative for him 
to get that slave manumitted completely by paying the remaining price, and if he does not have 
sufficient money to manumit him, then the price of the slave should be estimated justly, and he is to 
be allowed to work and earn the amount that will manumit him (without overburdening him)".
حَدَّثَنَا بِشْرُ بْنُ مُحَمَّدٍ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا سَعِيدُ بْنُ أَبِي عَرُوبَةَ، عَنْ قَتَادَةَ، عَنِ النَّضْرِ بْنِ أَنَسٍ، عَنْ بَشِيرِ بْنِ نَهِيكٍ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ مَنْ أَعْتَقَ شَقِيصًا مِنْ مَمْلُوكِهِ فَعَلَيْهِ خَلاَصُهُ فِي مَالِهِ، فَإِنْ لَمْ يَكُنْ لَهُ مَالٌ قُوِّمَ الْمَمْلُوكُ، قِيمَةَ عَدْلٍ ثُمَّ اسْتُسْعِيَ غَيْرَ مَشْقُوقٍ عَلَيْهِ ‏"‏‏.‏