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
Abu Mas'ud al-Badri reported

I was beating my slave with a whip when I heard a voice behind me: Understand, Abu Masud; but I did not recognise the voice due to intense anger. He (Abu Mas'ud) reported: As he came near me (I found) that he was the Messenger of Allah (ﷺ) and he was saying: Bear in mind, Abu Mas'ud; bear in mind. Abu Mas'ud. He (Aba Maslad) said: threw the whip from my hand. Thereupon he (the Holy Prophet) said: Bear in mind, Abu Mas'ud; verily Allah has more dominance upon you than you have upon your slave. I (then) said: I would never beat my servant in future.