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 (ﷺ) , 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.

وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ - وَاللَّفْظُ لاِبْنِ الْمُثَنَّى - قَالاَ حَدَّثَنَا ابْنُ، أَبِي عَدِيٍّ عَنْ شُعْبَةَ، عَنْ سُلَيْمَانَ، عَنْ إِبْرَاهِيمَ التَّيْمِيِّ، عَنْ أَبِيهِ، عَنْ أَبِي مَسْعُودٍ، أَنَّهُ كَانَ يَضْرِبُ غُلاَمَهُ فَجَعَلَ يَقُولُ أَعُوذُ بِاللَّهِ - قَالَ - فَجَعَلَ يَضْرِبُهُ فَقَالَ أَعُوذُ بِرَسُولِ اللَّهِ ‏.‏ فَتَرَكَهُ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏

‏ وَاللَّهِ لَلَّهُ أَقْدَرُ عَلَيْكَ مِنْكَ عَلَيْهِ ‏

‏ ‏.‏ قَالَ فَأَعْتَقَهُ ‏.‏