كتاب العتق
20  
The Book of Emancipating Slaves
(2)
Chapter: A slave working to pay off the other half
(2)
باب ذِكْرِ سِعَايَةِ الْعَبْدِ ‏‏
Sahih Muslim 1502

Abu Huraira (Allah be pleased with him) reported Allah's Messenger (ﷺ) as saying:

The slave who is jointly owned by two persons, and is emancipated by one of them, (this one) has liability (upon him to secure complete freedom for that slave).
وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ - وَاللَّفْظُ لاِبْنِ الْمُثَنَّى - قَالاَ حَدَّثَنَا مُحَمَّدُ، بْنُ جَعْفَرٍ حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنِ النَّضْرِ بْنِ أَنَسٍ، عَنْ بَشِيرِ بْنِ نَهِيكٍ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ فِي الْمَمْلُوكِ بَيْنَ الرَّجُلَيْنِ فَيُعْتِقُ أَحَدُهُمَا قَالَ ‏ "‏ يَضْمَنُ‏"‏ ‏.‏
Reference : Sahih Muslim 1502
In-book reference : Book 20, Hadith 3
USC-MSA web (English) reference : Book 9, Hadith 3580
  (deprecated numbering scheme)