(8) باب صُحْبَةِ الْمَمَالِيكِ وَكَفَّارَةِ مَنْ لَطَمَ عَبْدَهُ
Abu Mas'ud reported that he had been beating his slave and he had been saying:
I seek refuge with Allah, but he continued beating him, whereupon he said: I seek refuge with Allah's Messenger, and he spared him. Thereupon Allah's Messenger (ﷺ) said: By Allah, God has more dominance over you than you have over him (the slave). He said that he set him free.
Reference: Sahih Muslim 1659 d
In-book reference: Book 27, Hadith 57
USC-MSA web (English) reference(deprecated numbering scheme): Book 15, Hadith 4089