117
They demanded hat either Allah Himself should come before them and say, "This is My Book and these are My Instructions for you to follow." Or, He should show such a Sign to them as would conclusively demonstrate that Muhammad (Allah's peace be upon him) was really a Messenger of Allah and that what he presented was revealed to him by Allah.
118
That is, "The objections and demands of those who are opposing the Truth today are not new. These are exactly the same as have always been put forward by those who go astray from the Right Way, as all the wicked people of all ages think alike and follow the same line of argument."
119
The demand that Allah Himself should speak to them was so absurd that it needed no reply. As to the other demand that Allah should show them a Sign, Allah answers that He has shown many clear Signs but those who are not inclined to believe cannot see them.
120
Not to speak of the other Signs, the most conspicuous Sign was the personality of Muhammad himself (Allah's peace be upon him). They knew everything about his life before Prophethood; the conditions of his country and nation and the circumstances and environment under which he was brought up and how he spent the first forty years of his life before his appointment as a Prophet;