And if We had made him [i.e., the messenger] an angel, We would have made him [appear as] a man, and We would have covered them with that in which they cover themselves [i.e., confusion and doubt].
(And even if We had sent down unto you a Message written on paper so that they could touch it with their hands,) meaning, if they saw this Message's descent and were eye- witnesses to that,
(the disbelievers would have said: "This is nothing but obvious magic!") This is similar to Allah's description of the disbelievers' defiance of facts and truth,
The third verse (8) was also revealed because of an event which concerns this very ` Abdullah ibn Abi Umaiyyah who, accompanied by Nadr ibn al-Harith and Nawfal ibn Khalid ؓ ، came to the Holy Prophet ﷺ . This time their demand was: ` We shall believe in you only when you go and bring a book from the heavens and let four angels come along with it to testify that the book was from none but Allah and that you are the Messenger of Allah.'
One answer Allah gave to them was that by making such demands, these heedless people were inviting their own destruction, because the Divine law is that, should a people ask their prophet to show a miracle of their choice, and as a result of their demand, such miracle is shown by the power and will of Allah, then, should they, even then, remain reluctant to believe and accept faith any longer, they are destroyed by a mass general punishment. These particular people of Makkah were really not making their demands as based on any good intentions, which may have at the least given some hope of their accepting the truth. Therefore, it was said: وَلَوْ أَنزَلْنَا مَلَكًا لَّقُضِيَ الْأَمْرُ ثُمَّ لَا يُنظَرُونَ (And had We sent down an angel, the whole matter would have been finished). In other words, it means ` If We do send the miracle they demand, that is, send an angel, then, these people who are not the kind who would accept truth will still act contrary and hostile even after having seen the miracle, then, the Divine command to have them destroyed would stand activated. Since they would be given no respite after that hap-pens, therefore, they should understand that the fact of not showing the miracle demanded by them spells out real good for them, without which they would be nowhere.
The reason for a man going astray in this world is that here he has complete freedom to reject the Truth. He even has the opportunity to give fine justifications for erroneous thoughts, words and deeds. Man enjoys full freedom in this world of trial to accept or reject the Truth as he pleases. If the preacher of God’s word appears in the shape of an ordinary man, the ‘reason’ given for ignoring him could be that his effectiveness hinges on a talent for leadership and has nothing to do with Truth or righteousness. Similarly, if a book complete in every detail, comes down from the sky, he will say, ‘This is mere magic,’ to justify his rejection of it. The people of Makkah used to ask, if the Prophet was appointed to convey God’s message, why God’s angels were not with him to testify. A man talks like this because he is not serious about the call of God’s message. If he is serious, he will immediately come to know that this world is a place of trial. The test can be carried out only when realities are hidden behind a curtain. If the hidden realities were revealed and God and His angels made their appearance, there would be no question of prophethood or of giving the call of Truth, because thereafter nobody would dare to deny the realities. In the present world, because of their devotion to externals, people are unable to recognise the Messenger of God from the importance of his message. God’s Messenger appears to them like an ordinary man suddenly emerging and claiming very high status. They assess him on the basis of his outward appearance and, finding him insignificant in that respect, they deny him.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.