The Quran frequently documents the skepticism of nonbelievers, detailing their demands to see God directly, to be shown angels, or to receive a physical book sent straight from heaven as proof of divine revelation. [1, 2, 3, 4, 5]

Specific verses illustrating these demands include:

1. Demanding a physical book from heaven

“Those who have no knowledge also say, ‘If only God would speak to us!’ or ‘If only a miraculous sign would come to us!’ People before them said the same things: their hearts are all alike. We have made Our signs clear enough to those who have solid faith.”
— Surah Al-Baqarah 2:118 [1]

“The People of the Scripture ask you to bring down to them a book from the sky. But they asked Moses for [something] greater than that and said, ‘Show us Allah outright,’ so the thunderous blast struck them for their wrongdoing.”
— Surah An-Nisa 4:153

“They say, ‘We will not believe for you [Muhammad] until you make a spring gush out of the ground for us; or until you have a garden of date palms and vines, and make rivers pour through them; or make the sky fall on us in pieces, as you claimed will happen; or bring God and the angels before us face to face; or have a house made of gold; or ascend into the sky– even then, we will not believe in your ascension until you send a real book down for us to read.’ Say, ‘Glory be to my Lord! Am anything but a mortal, a messenger?’ The only thing that kept these people from believing, when guidance came to them, was that they said, ‘How could God have sent a human being as a messenger?’ Say, ‘If there were angels walking about on earth, feeling at home, We would have sent them an angel from Heaven as a messenger.’ Say, ‘God is witness enough between me and you. He knows and observes His servants well.’” — Surah Al-Isra 17:90-96 [1]

2. Demanding to see God or Angels

“Those who have no knowledge also say, ‘If only God would speak to us!’ or ‘If only a miraculous sign would come to us!’ People before them said the same things: their hearts are all alike. We have made Our signs clear enough to those who have solid faith.”
— Surah Al-Baqarah 2:118 [1]

“And those who do not expect the meeting with Us say, ‘Why were not angels sent down to us, or [why] do we not see our Lord?’ They have certainly become arrogant within themselves and [become] insolent with great insolence.”
— Surah Al-Furqan 25:21

3. The Quranic response to these demands
In each of these instances, the Quran instructs the Prophet to respond that he is merely a human messenger and a warner, and that true signs are entirely up to Allah. Furthermore, the Quran states that even if their demands for direct, supernatural revelations were met, their hearts are such that they still would not believe: [1, 2, 3, 4]

“Even if We had sent down to them the angels [themselves] and the dead had spoken to them and We had gathered together every [created] thing in front of them, they would not believe unless Allah should will. But most of them are ignorant.”
— Surah Al-An’am 6:111 [1]