It is a universal truth that every action has its reaction. It means “if it is so, then it will be so” as its reaction. For example, if someone commits a crime, then he will be punished, if he follows the law of his country, he will be rewarded, if he serves his parents, he will be well-wished, and if he teases them, then he will be cursed. Similarly, if he touches the fire, it will burn him, if he handles the ice, it will makes him cold, and if he eats poison, then he will die etc.

Infect, reaction for something is a natural law that is inevitable and cannot be changed; as it is mentioned in the Holy Qur’an, “Then, can they expect aught save the treatment of the folk of old? Thou wilt not find for Allah’s way of treatment any substitute, nor wilt thou find for Allah’s way of treatment aught of power to change. (Al-Fatir:43)
Natural law has two parts, first is a Term or condition it means” If it is so” and second one “then it will be so” is its reward. It means that if the first part is found, then the second one will also be found surely. 

As we know that every regime has its constitution and a penal code for her citizens. According to it, the honorable Judges decide the cases. If someone disobeys the Law of his country, then he is captured and be punished.

Similarly, this universe is infect Allah’s “country” and He is absolute and powerful King of His regime having no partner in His sovereignty. The holy Quran reveals,” Blessed is He in Whose hand is the Sovereignty, and He is Able to do all things. Who hath created life and death that He may try you, which of you is best in conduct; and He is the Mighty, the Forgiving.”(The Sovereignty: 2)Also reveals,” Unto Allah belongeth the Sovereignty of the heavens and the earth. Allah is Able to do all things. (Family of Imran: 189)

He created man for His worship and made a constitution for him that is “Religion of Islam” as Ordains in the Holy Qur’an, “This day have I perfected your religion for you and completed My favour unto you, and have chosen for you as religion AL-ISLAM.(Il-Maidah:3). These verses reveal that ‘the constitution’ of the Regime of Allah for mankind is only Islam and not other religion except it as the holy Qur’an reveals, “And whoso seeketh as religion other then the Surrender (to Allah)(Al-Islam), it will not be accepted from him, and he will be a loser in the Hereafter.”(Family of Imran: 85).

He gave the warning to man that if he obeys the orders of Allah, then he will be awarded Paradise, and if he violates them, then he will be thrown in Hell. He will set up a “Highly authorized Supreme Court” at the Day of Judgment and He, His highness will be the Chief Justice of His Royal Court and will decide the cases. The decision at the Day of Judgment about mankind is infect, the reaction of his actions that he made in this world. As it is said “As you sow, so shall you reap”.

Some people deny this decision and say that when the man will be dead and becomes dust or ashes, (as the Hindus set their dead bodies on fire then shed ashes in the river), whether it is possible to become alive again? So, Almighty Allah Ordains, “And they say: when we are bones and fragments, shall we, forsooth, be raised up as a new creation?

Say: Be ye stones or iron Or some created thing that is yet greater in your thoughts! then they will say: Who shall bring us back (to life)? Say: He Who created at the first. Then will say shake their heads at thee, and say: When will it be? Say: it will perhaps be soon. A Day when He will call you and ye will answer with His praise, and ye will think that ye have tarried but a little while. (The Children of Israel: 52)

It means that all the people will be brought back to lives again, and then they will be presented before Allah, where they will find reward or punishment for their actions. The Holy Qur’an reveals,” Every soul will taste of death. And ye will be paid on the Day of Resurrection only that which ye have fairly earned. Whoso is removed from the Fire and is made to enter Paradise, he indeed is triumphant. The life of this world is but comfort of illusion. (The Family of Imran: 185)

It is mentioned before that if someone violates the laws of Nature is captured and will be punished. So, how will he be punished at the Day of Resurrection, the holy Qur’an reveals about it, “But as for him who is given his record in his left hand, he will say: Oh, would that I had not been given my book. And knew not what my reckoning! Oh, would that I had been death! My wealth hath not availed me; my power hath gone from me. (It will be said): Take him and fetter him. And then expose him to hellfire, and then insert him in a chain whereof the length is seventy cubits.Lo! He used not to believe in Allah the Tremendous, and urged not on the feeding of the wretched, thereof hath he no lover here this day, Non any food save filth Which none but sinners eat.”(The Reality: 35)

Also reveals,” The guilty will be known by their marks, and will be taken by the forelocks and the feat. Which is it, of the favours of your Lord, that ye deny? This is Hell which they go circling round between it and fierce, boiling water” (The Beneficient: 45).

So, it is necessary for everyone to obey all the commands of Allah Almighty so that he may get the immense reward from Allah and pass a successful life forever. The holy Qur’an reveals, “

(And ) those who believe and do good works are the best of created beings. Their reward is with their Lord: Gardens of Eden underneath which rivers flow, wherein they dwell forever. Allah hath pleasure in them and they have pleasure in Him. (This is (in store) for him who fearth his Lord.(Al-Bayyenah: 8 )