Fear of God
What is sin? It is to go against the will of God and to violate His instructions given to mankind through prophets and especially through the Holy Prophet, sallallaho alaihi wa sallam. Sin is to reject boldly the guidance that is given to them and which they have understood properly. He who violates the commandments of God in connection with this guidance and acts mischievously attracts the wrath. The consequences of this temerity and boldness is not only this much that he will go to the hell in the next world; in this world also he will have to taste punishment and he will be humiliated.
Same is the case with the authorities that be in the worldly affairs. They promulgate a law and make it known to the people. Later on who ever is found violating it, he is charged and punished. But so far as the punishment of the worldly laws is concerned, one can manoeuver to leave that domain and go elsewhere and get rid of them. For example if one violates the law of the British Government, he can run to France or to the domain of Kabul and thus he can save himself from the punishment. But where can a man flee after the violation of the commandments of God, for, the earth and the sky that we see belong to Him. There is no earth and no sky elsewhere, belonging to someone else where one may seek refuge. This is why it is very essential that one must always have the fear of God and never show boldness in violating His commandments. Sin is a very bad thing and when a man becomes bold and does not fear the violation of the commandments, then the wrath of God descends on him in this world as well as in the next world.
(Malfoozat vol. 6, pg. 392)