Al-Adab Al-Mufrad, Book 9, Hadith 22 (In-Book) ⓘ
Ibn 'Umar said, "I heard the Prophet, may Allah bless him and grant him peace, say, 'The expiation for someone who slaps his slave or beats him more than he deserves is to set him free.'"
حَدَّثَنَا عَمْرُو بْنُ عَوْنٍ، وَمُسَدَّدٌ، قَالاَ: حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ فِرَاسٍ، عَنْ أَبِي صَالِحٍ، عَنْ زَاذَانَ، عَنِ ابْنِ عُمَرَ قَالَ: سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ: مَنْ لَطَمَ عَبْدَهُ أَوْ ضَرَبَهُ حَدًّا لَمْ يَأْتِهِ، فَكَفَّارَتُهُ عِتْقُهُ.
also referenced under: Hadith 177 (Reference) & Book 9, Hadith 177 (English)