Those people who demand physical miracles do not truly appreciate the great favour God has granted them with the Qur’ān. He bestowed this from on high so as to guide them:
“Is it not sufficient for them that We have sent down to you the Book (the Quran) which is recited to them? Verily, herein is mercy and a reminder (or an admonition) for a people who believe.” Suuratu Al-Ankabuut 29:51
Their demands reflect an attitude of discontent with God’s great favour when, in fact, no amount of thanks and gratitude is adequate. Is it not enough for them that they actually live with this Qur’ān as it is revealed from on high. It tells them about what they feel within themselves, explains what takes place around them and makes them feel that God is watching over them, taking care of them, relating historical accounts that should educate them? What is man but a little creature, lost in God’s great universe? Indeed, mankind, the earth they live on and the sun around which it moves are no more than little particles in this great expanse. They are held in place only by God’s power. Yet He honours them, bestowing His revelations so that they are recited to them, and they are neither thankful nor satisfied.
“Verily, herein is mercy and a reminder (or an admonition) for a people who believe.”(Verse 51) It is only believers who feel this grace. They appreciate His blessings as He invites them to come to Him when He is the Most High, the Supreme. Such people benefit by the Qur’ān, because it lives in their hearts, opens its treasures to them and enlightens their souls with true knowledge and supreme light.
Those who do not feel any of this are the ones who demand a physical miracle so that they can accept this Qur’ān as true. These are blind people whose hearts do not open up to light. There is no use trying to argue with such people. Hence, the Prophet is instructed to leave a decision about them to God Almighty:
“Say: God is sufficient as a witness between me and you! He knows all that is in the heavens and the earth; and they who believe in falsehood and disbelieve in God will certainly be the losers.“(Suuratu Al-Ankabuut 29:Verse 52)
A witness who knows all that takes place in the heavens and earth gives the best and greatest testimony. It is He who knows that their situation is false: “They who believe in falsehood and disbelieve in God will certainly be the losers.” (Verse 52) They are the absolute losers; they are the ones who forego everything. They lose both this world and the life to come, as also themselves, divine guidance, righteousness, reassurance, truth and light. To believe in God is, in itself a great gain, and to be rewarded for it is by God’s grace. Belief provides reassurance and a steady footing along the way, steadfastness in the face of adversity, trust in God’s help and protection, and confidence as to the eventual outcome. This is indeed a great gain, and it is what the unbelievers lose.
Taken from: In the shade of The Qur’an Volume_13_surahs_26-32 page 265-6