King's duty---From Adi parva of Mahabharta

An ascetic tells his son ,
                                    If a king doesnot protect us we fare ill.We cannot perform our religious rites according to our desire .But protected by righteous sovereigns we attain immense merit and they are entitled to a share there of.
The king punishes offenders and fear of punishments leads to peace and people do their duties and perform their rites undisturbed.
The king protects sacrifises [yagas] from disturbance and sacrifices pleases gods.The gods cause rain and rain produces grains which is always useful to man .