(5) باب إِذَا أَعْتَقَ نَصِيبًا فِي عَبْدٍ، وَلَيْسَ لَهُ مَالٌ اسْتُسْعِيَ الْعَبْدُ غَيْرَ مَشْقُوقٍ عَلَيْ، عَلَى نَحْوِ الْكِتَابَةِه
Narrated Abu Huraira:
The Prophet (ﷺ) said, "Whoever frees his portion of a common slave should free the slave completely by paying the rest of his price from his money if he has enough money; otherwise the price of the slave is to be estimated and the slave is to be helped to work without hardship till he pays the rest of his price."
Reference: Sahih al-Bukhari 2527
In-book reference: Book 49, Hadith 12
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 46, Hadith 704