Hadith on Freedom: The expiation for the sin of beating a slave is to free him

Zadhan reported: Ibn Umar called his boy and he found traces of a beating upon his back. He said to him, “I have hurt you.” He said, “No.” But Ibn Umar said, “You are free.” Then he took hold of some dust from the
earth and he said, “There is no reward for me, even equal to this weight. I heard the Messenger of Allah, peace and blessing be upon him, say: Whoever strikes his slave without limit or slaps him, then verily the expiation for the sin is to emancipate him.”

[Sahih Muslim, Book 15, Number 4079]

عَنْ زَاذَانَ أَنَّ ابْنَ عُمَرَ دَعَا بِغُلَامٍ لَهُ فَرَأَى بِظَهْرِهِ أَثَرًا فَقَالَ لَهُ أَوْجَعْتُكَ قَالَ لَا قَالَ فَأَنْتَ عَتِيقٌ قَالَ ثُمَّ أَخَذَ شَيْئًا مِنْ الْأَرْضِ فَقَالَ مَا لِي فِيهِ مِنْ الْأَجْرِ مَا يَزِنُ هَذَا إِنِّي  سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ مَنْ ضَرَبَ غُلَامًا لَهُ حَدًّا لَمْ يَأْتِهِ أَوْ لَطَمَهُ فَإِنَّ كَفَّارَتَهُ أَنْ يُعْتِقَهُ

1657 صحيح مسلم كِتَاب الْأَيْمَانِ من لطم مملوكه أو ضربه فكفارته أن يعتقه