Prophet Muhammad (PBUH) once came across a slave who was grinding grains with a grinding mill by hand. As he continued working, tears rolled down his face. This made Prophet (PBUH) very concerned. He went to the slave and asked him about the reason of his crying. He replied, “I am very ill.
My master is very insensitive and if I do not finish my task, he will beat me very ferociously”. After hearing this, the Prophet Muhammad (PBUH) offered His help and said “Always tell me if you need any grains to mill. I will do your task for you.”