Sunan Ibn Majah 3691
It was narrated from Abu Bakr Siddiq(RA) that the Messenger of Allah(ﷺ) said:
"No person who mistreats his slave will enter Paradise." They said: " O Messenger of Allah, did you  not tell us that this nation will have more slaves and orphans than any other nation?" He said: " Yes, so be as kind to them as you are to your own children, and feed them with the same food that you eat." They said: "What will benefit us in this world?" He said: "A horse that is kept ready for fighting in the cause of Allah, and your slave to take care of you, and if he performs prayer, then he is your brother(in Islam)."
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَعَلِيُّ بْنُ مُحَمَّدٍ، قَالاَ حَدَّثَنَا إِسْحَاقُ بْنُ سُلَيْمَانَ، عَنْ مُغِيرَةَ بْنِ مُسْلِمٍ، عَنْ فَرْقَدٍ السَّبَخِيِّ، عَنْ مُرَّةَ الطَّيِّبِ، عَنْ أَبِي بَكْرٍ الصِّدِّيقِ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ لاَ يَدْخُلُ الْجَنَّةَ سَيِّئُ الْمَلَكَةِ ‏"‏ ‏.‏ قَالُوا يَا رَسُولَ اللَّهِ أَلَيْسَ أَخْبَرْتَنَا أَنَّ هَذِهِ الأُمَّةَ أَكْثَرُ الأُمَمِ مَمْلُوكِينَ وَيَتَامَى قَالَ ‏"‏ نَعَمْ فَأَكْرِمُوهُمْ كَكَرَامَةِ أَوْلاَدِكُمْ وَأَطْعِمُوهُمْ مِمَّا تَأْكُلُونَ ‏"‏ ‏.‏ قَالُوا فَمَا يَنْفَعُنَا فِي الدُّنْيَا قَالَ ‏"‏ فَرَسٌ تَرْتَبِطُهُ تُقَاتِلُ عَلَيْهِ فِي سَبِيلِ اللَّهِ مَمْلُوكُكَ يَكْفِيكَ فَإِذَا صَلَّى فَهُوَ أَخُوكَ ‏"‏ ‏.‏