كتاب العتق
20
The Book of Emancipating Slaves
(6)
Chapter: The virtue of manumitting slaves
(6)
باب فَضْلِ الْعِتْقِ ‏‏

Abu Huraira (Allah be pleased with him) reported:

I heard Allah's Messenger (ﷺ) as saying: He who emancipates a believing slave. Allah will set free from Fire his every limb for every limb of his (slave's), even his private parts for his.
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، عَنِ ابْنِ الْهَادِ، عَنْ عُمَرَ بْنِ عَلِيِّ بْنِ حُسَيْنٍ، عَنْ سَعِيدِ ابْنِ مَرْجَانَةَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ مَنْ أَعْتَقَ رَقَبَةً مُؤْمِنَةً أَعْتَقَ اللَّهُ بِكُلِّ عُضْوٍ مِنْهُ عُضْوًا مِنَ النَّارِ حَتَّى يُعْتِقَ فَرْجَهُ بِفَرْجِهِ‏"‏ ‏.‏
Reference : Sahih Muslim 1509 c
In-book reference : Book 20, Hadith 27
USC-MSA web (English) reference : Book 9, Hadith 3604
  (deprecated numbering scheme)