(5) باب إِذَا أَعْتَقَ نَصِيبًا فِي عَبْدٍ، وَلَيْسَ لَهُ مَالٌ اسْتُسْعِيَ الْعَبْدُ غَيْرَ مَشْقُوقٍ عَلَيْ، عَلَى نَحْوِ الْكِتَابَةِه
Narrated Abu Huraira:
That the Prophet (ﷺ) said, "Whoever frees his portion of a (common) slave."
Reference: Sahih al-Bukhari 2526
In-book reference: Book 49, Hadith 11
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 46, Hadith 703