Mara treated the fisherman in a harsh way because he caused violence by catching fish in tank and he warned him not to repeat the same as it was the order by the king as well as by Goddess to look after the place peacefully without non-violence. But Mara spoke softly to the visitor and he becomes a solution to his problem by offering water for his fields. But he told that it should happen not according to his wish but according to the laws. Not only did he assured him but also offered food and shelter in his house as a guest. So, we can see that Mara used to behave differently according to the behaviour of the persons.
