Arabic text
عن أبي مسعود البَدْري رضي الله عنه قال: كنت أضرب غُلاما لي بالسَّوْط، فسمعت صوتا من خَلفِي: «اعلم أبَا مسعود» فلم أفْهَم الصَّوت من الغَضَب، فلمَّا دَنَا مِنِّي إذا هو رسول الله صلى الله عليه وسلم فإذا هو يقول: «اعلم أبَا مسعود أن الله أقْدَرُ عليك مِنْك على هذا الغُلام». فقلت: لا أَضرب مملوكا بعده أبدًا. وفي رواية: فسقط السَّوط من يَدي من هَيْبَتِه. وفي رواية: فقلت: يا رسول الله، هو حُرٌّ لوجه الله تعالى، فقال: «أمَا لو لم تفعل، لَلَفَحَتْكَ النَّار، أو لَمَسَّتْكَ النَّار».
Translation
Abu Mas‘ūd al-Badri (may Allah be pleased with him) reported: I was whipping a slave boy of mine when I heard a voice behind me saying: "Bear in mind, O Abu Mas‘ūd!" I did not recognize the voice out of anger. When he came near me, I found that it was the Messenger of Allah (may Allah's peace and blessings be upon him) who was saying: "Bear in mind, O Abu Mas‘ūd, that Allah has more power over you than you have over this boy." I said: "I will never beat a slave ever again." In another narration: "The whip dropped from my hand in awe of him." And in yet another narration: "I said: 'O Messenger of Allah, he is free for the sake of Allah, the Exalted.' Thereupon he said: 'If you had not done so (i.e. free him), the fire would have scorched you, or the fire would have touched you."
Explanation
Abu Mas‘ūd (may Allah be pleased with him) was beating his slave boy with a whip. He heard a voice from behind rebuking him but he could not identify the speaker. When the speaker came near to him, he recognized that it was the voice of the Messenger of Allah (may Allah's peace and blessings be upon him) reminding him of the power of Allah, the Almighty, by saying: "Bear in mind, Abu Mas‘ūd, that Allah has more power over you than you have over this boy." So when he heard what the Prophet (may Allah's peace and blessings be upon him) said and his warning against abusing the weak, the whip fell from his hand in awe of the Messenger of Allah, and he promised him that he would never abuse any slave after that. Also, after he heard the Prophet's rebuke and warning, he immediately set the slave free to expiate for beating him. Thereupon, the Prophet (may Allah's peace and blessings be upon him) said: "If you had not freed him, the fire would have afflicted you on the Day of Resurrection because of the evilness of your deed."
Source: HadeethEnc.com