Hadith: You are a person who has remnants of the ignorant pre-Islamic manners. Your slaves are your brothers and servants whom Allah has placed under your authority. He who has his brother under his authority should feed him from whatever he eats, dress him with whatever he wears, and not assign burdensome and difficult tasks to them that are beyond their capacity. If you do this then help them

عن المعرور بن سويد، قال: رأيت أبا ذر رضي الله عنه وعليه حلة وعلى غلامه مثلها، فسألته عن ذلك، فذكر أنه قد سابَّ رجلا ًعلى عهد رسول الله صلى الله عليه وسلم فَعَيَّره بأمه، فقال النبي صلى الله عليه وسلم : «إنك امْرُؤٌ فيك جاهلية هم إِخْوَانُكُمْ وخَوَلُكُمْ جعلهم الله تحت أيديكم، فمن كان أخوه تحت يده، فليُطعمه مما يأكل، وليُلْبِسْهُ مما يلبس، ولا تُكَلِّفُوهُمْ مَا يَغْلِبُهُمْ، فَإِنْ كَلَّفْتُمُوهُمْ فَأَعِينُوهُمْ ».
[صحيح] - [متفق عليه]

Al-Ma‘rūr ibn Suwayd reported: I saw Abu Tharr (may Allah be pleased with him) wearing a nice clothes, and his slave was wearing a similarly nice clothes also. I asked him about this and he said that he had exchanged harsh words with a person during the lifetime of the Messenger of Allah (may Allah's peace and blessings be upon him) and insulted him by making an offensive reference to his mother. That person came to the Messenger of Allah (may Allah's peace and blessings be upon him) and made mention of that (abuse) to him. Then the Messenger of Allah (may Allah's peace and blessings be upon him) said: "You are a person who has remnants of the ignorant pre-Islamic manners. Your slaves are your brothers and servants whom Allah has placed under your authority. He who has his brother under his authority should feed him from whatever he eats, dress him with whatever he wears, and not assign burdensome and difficult tasks to them that are beyond their capacity. If you do this then help them."
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

This Hadīth indicates an encouragement to deal with servants and slaves in a good manner especially in terms of their clothing and food. It also advises Muslims to not overburden them with difficult tasks that go beyond their capacity unless you were to help them accomplish these tasks. The Hadīth also indicates a severe threat for those who demean, humiliate and insult servants and slaves in any way because they are our brothers in Islam.