What is it that makes it necessary for God to show people a miracle?

It may be suggested that when people do see a miracle, they are more likely to believe in God Almighty and worship Him as He should be worshipped. Therefore, a miracle may be the short cut for making people believe in God and implement His law. However, historical facts show otherwise. When miracles were vouchsafed to earlier prophets, their communities accused them of sorcery and were even more determined to reject the faith preached by those prophets. Thus, we have the statement of Pharaoh and his people, reported in the Quran, in which they challenged Moses to a contest of sorcery.

"He said: Have you come to drive us out of our land with your magic, O Moses? We will certainly come up with sorcery equal to yours. Fix, then, an appointment which we will not fail to keep and neither will you, in a place assigned’” Quran 20: 57-8). Elsewhere in the Quran, Moses was told, "Whatever sign you bring in order to bewitch us, we shall not believe in you" (7: 132).

So miracles are not the answer to people's rejection of the faith. They can be shown the clearest of signs and miracles and yet continue to deny God and His message. But God does not give people the challenge of a miracle out of mercy and grace. He has established a rule, which is applicable to all people, when they are shown such a miracle. If they continue to disbelieve in Him after He has given them the miracles they ask for, they will be destroyed forthwith. They will not have another chance. That is because they actually condemn themselves to destruction by their continued rejection. Rather than put people to this test, God gives them an extended chance to believe in Him. The means to win them over to faith are already in place. He has sent them infallible guidance embodied in the Quran. They need only approach the Quran with clear minds to accept its argument and believe in its message. At any time in man's life, there are moments of clear vision. If a person makes use of such moments, he is sure to accept God’s guidance and believes in Him.

Moreover, miracles are present in the world around us at every moment in life. We need only reflect on what takes place in the universe, in human life, and within ourselves. God says in the Quran, "Surely, in the earth there are signs for people with certainty of faith, and indeed within your own selves. Will you not see?"

Look at the birth of every child and reflect on the development of a human being from the moment of conception to the moment of birth and continue your reflection to encompass man's life in this world. The miraculous aspects in all this are so numerous and clear that we have to acknowledge God’s own works. [Reflect on] how your heart continues to beat all the time, doing a process which is so essential for your life. Reflect also on how your stomach accepts such a great variety of food which you eat at the same time without giving a thought to whether what you are eating can be digested by the same mechanism. Then reflect on how your stomach can make use of it all and transform it into nourishment. Reflect on other aspects of your existence and the existence of the world around you. Reflect on the fine balance, which God has created to ensure that life continues without one side of it overwhelming the rest. All this is miraculous. Why do we need a material miracle which could signal our own destruction?
And God Almighty knows best.