Musnad Ahmad 75
It was narrated that Abu Bakr as Siddeeq said:
The Messenger of Allah (ﷺ) said: “No one who mistreats his slaves will enter Paradise.` Aman said: O Messenger of Allah, didn't you tell us that this ummah is the greatest in numbers of slaves and orphans? He said: `Yes, so treat them kindly as you treat your children and feed them from what you eat.` They said: What could benefit us in this world, O Messenger of Allah? He said: “A good horse which you keep ready for fighting for the sake of Allah and a slave to take care of you. If he prays (becomes Muslim), then he is your brother, if he prays, then he is your brother.”
حَدَّثَنَا إِسْحَاقُ بْنُ سُلَيْمَانَ، قَالَ سَمِعْتُ الْمُغِيرَةَ بْنَ مُسْلِمٍ أَبَا سَلَمَةَ، عَنْ فَرْقَدٍ السَّبَخِيِّ، عَنْ مُرَّةَ الطَّيِّبِ، عَنْ أَبِي بَكْرٍ الصِّدِّيقِ، رَضِيَ اللَّهُ عَنْهُ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَا يَدْخُلُ الْجَنَّةَ سَيِّئُ الْمَلَكَةِ فَقَالَ رَجُلٌ يَا رَسُولَ اللَّهِ أَلَيْسَ أَخْبَرْتَنَا أَنَّ هَذِهِ الْأُمَّةَ أَكْثَرُ الْأُمَمِ مَمْلُوكِينَ وَأَيْتَامًا قَالَ بَلَى فَأَكْرِمُوهُمْ كَرَامَةَ أَوْلَادِكُمْ وَأَطْعِمُوهُمْ مِمَّا تَأْكُلُونَ قَالُوا فَمَا يَنْفَعُنَا فِي الدُّنْيَا يَا رَسُولَ اللَّهِ قَالَ فَرَسٌ صَالِحٌ تَرْتَبِطُهُ تُقَاتِلُ عَلَيْهِ فِي سَبِيلِ اللَّهِ وَمَمْلُوكٌ يَكْفِيكَ فَإِذَا صَلَّى فَهُوَ أَخُوكَ‏.‏