It is essential to feed the slave, clothe him (properly) and not burden him with work which is beyond his power. (Using translation from Muslim 1662)
قَالَ رَسُولُ اللهِ ﷺ لِلْمَمْلُوكِ طَعَامُهُ وَكِسْوَتُهُ وَلَا يُكَلَّفُ مِنَ الْعَمَلِ مَا لَا يُطِيقُ