The Jews, the Christians and the mushrikin used to deny the prophethood of Sayyidna Muhammad ﷺ and some of them did so out of sheer malevolence. In order to feel triumphant in this obstinacy, they would make absurd and impossible demands, two of which have been mentioned here. To begin with, they insisted that Allah Himself should speak to them, either directly as He speaks to the angels, or through the angels as He speaks to the prophets, and that He should Himself proclaim his injunctions to them so as to make the intervention of a new prophet unnecessary, or should at least announce that He had sent Sayyidna Muhammad ﷺ as a prophet, thus making it easy for them to have faith in him and to follow his guidance. Should Allah choose not to accept this demand, they were ready with another -- that is, Allah should send them a sign or proof in confirmation of his prophethood.
In reply to them, Allah puts this demand down as being no more than a foolish custom which has all along been unthinkingly practised by ignorant people even in the earlier ages. Then, the verse traces the origin of this demand to a distortion of the heart, in respect of which all the ignorant people, past or present, are alike, hence the parrot-like repetition of the same demand throughout the ages.
The first of these demands was, on the face of it, silly enough, for, with all the grossness of their minds and hearts, they had the audacity to place themselves on the level of angels and prophets. So, the Holy Qur'an dismisses it as being unworthy of a reply. But in answer to the other demand, Allah reminds them that He has sent, not one, but a number of clear signs and proofs to confirm and establish the prophethood of Sayyidna Muhammad ﷺ . But these signs and proofs can be of help only to those who sincerely wish to know the truth and to attain certitude. As for those who are not in search of the truth, but enjoy being stuck in their malice and obstinacy, there is no help for them.
At this point, we had better say a word to resolve a difficulty that is likely to arise. The Jews and the Christians were the People of the Book", and some of them were men of learning, and yet Allah calls them ignorant. Why? The reason is that although Allah had sent such a large number of clear signs and definite proofs to establish the prophethood of Sayyidna Muhammad .i" , yet they persisted in their denial. This is the mentality and the conduct of the ignorant.