كتاب الأيمان
27  
The Book of Oaths
(8)
Chapter: Treatment of slaves, and the expiation of one who slaps his slave
(8)
باب صُحْبَةِ الْمَمَالِيكِ وَكَفَّارَةِ مَنْ لَطَمَ عَبْدَهُ ‏‏
Sahih Muslim 1658 b

Hilal b. Yasaf reported that a person got angry and slapped his slave-girl. Thereupon Suwaid b. Muqarrin said to him:

You could find no other part (to slap) but the prominent part of her face. See I was one of the seven sons of Muqarrin, and we had but only one slave-girl. The youngest of us slapped her, and Allah's Messenger (ﷺ) commanded us to set her free. 2097
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَمُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، - وَاللَّفْظُ لأَبِي بَكْرٍ - قَالاَ حَدَّثَنَا ابْنُ إِدْرِيسَ، عَنْ حُصَيْنٍ، عَنْ هِلاَلِ بْنِ يَسَافٍ، قَالَ عَجِلَ شَيْخٌ فَلَطَمَ خَادِمًا لَهُ فَقَالَ لَهُ سُوَيْدُ بْنُ مُقَرِّنٍ عَجَزَ عَلَيْكَ إِلاَّ حُرُّ وَجْهِهَا لَقَدْ رَأَيْتُنِي سَابِعَ سَبْعَةٍ مِنْ بَنِي مُقَرِّنٍ مَا لَنَا خَادِمٌ إِلاَّ وَاحِدَةٌ لَطَمَهَا أَصْغَرُنَا فَأَمَرَنَا رَسُولُ اللَّهِ صلى الله عليه وسلم أَنْ نُعْتِقَهَا ‏.‏
Reference : Sahih Muslim 1658b
In-book reference : Book 27, Hadith 49
USC-MSA web (English) reference : Book 15, Hadith 4082
  (deprecated numbering scheme)