“If We will, We can send down a Sign to them from heaven, so their necks will be humbled to it. Never does there come to them an admonition from the Merciful One but they turn away from it. They will soon come to know the truth of that which they have been scoffing at.”
(Al-Qur’ān – 26:4-6)
It is not at all difficult for God to send a sign that would compel the unbelievers to believe and obey. If God does not send such a sign, it is not because this is beyond His power; rather it is because He does not want people to have Faith compulsively. Instead, God likes people to use their intellect and to recognise the Truth with the help of the signs in His Book as well as those spread throughout the Universe and within human beings themselves.
When people are convinced and their hearts testify that whatever has been taught by the Prophets of God is indeed true and all beliefs opposed to it are false, it is only then that they should decide to accept the Truth and reject falsehood. This is why God has granted man free-will and the power to choose between the right and wrong paths.
The remedy for those who remain contemptuously unresponsive to all rational efforts to direct them to the Truth is not to force them into submission with the help of Heavenly signs. Rather, what such people need is that the terrible consequences of their persistent denial of the Truth are fully impressed upon them.