حَدَّثَنِي أَبُو كَامِلٍ، فُضَيْلُ بْنُ حُسَيْنٍ الْجَحْدَرِيُّ حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ فِرَاسٍ، عَنْ ذَكْوَانَ أَبِي صَالِحٍ، عَنْ زَاذَانَ أَبِي عُمَرَ، قَالَ أَتَيْتُ ابْنَ عُمَرَ وَقَدْ أَعْتَقَ مَمْلُوكًا - قَالَ - فَأَخَذَ مِنَ الأَرْضِ عُودًا أَوْ شَيْئًا فَقَالَ مَا فِيهِ مِنَ الأَجْرِ مَا يَسْوَى هَذَا إِلاَّ أَنِّي سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏"‏ مَنْ لَطَمَ مَمْلُوكَهُ أَوْ ضَرَبَهُ فَكَفَّارَتُهُ أَنْ يُعْتِقَهُ ‏"‏.
Translation
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