Think of the psyche of an imposter prophet. If he or she is asked questions, especially relating to the supernatural, what kind of answers do you expect? Made up ones, of course! “Prophet, how many angels are there?” “John, there are 5 trillion angels.” “Why does the sun set?” “Because it’s humbling itself towards me.” Whatever you can imagine.

But let’s take an incident of Prophet Muhammad (ﷺ) that’s mentioned in the Qur’an:

“They ask you [O Muhammad] concerning the Ruh (Soul). Say: ‘It is one of the things, the knowledge of which is only with my Lord. And of knowledge, you (mankind) have been given very little.”

[Qur’an 17:85]

If he was an imposter and the author of the Qur’an, rather than God Himself, why expose himself by saying that he doesn’t know the answer? What would have been the loss for making something up? Would his followers ever find out if it was true or not? Obviously not. 

In another incident, he was asked by someone, “When will the Hour (Day of Judgment) be established?” The Prophet (ﷺ) replied, “The one who is asked about it does not know more than the questioner does…” [Sahih Bukhari]

Think about that – he could’ve said anything! Could’ve said “5,000 years” and all his followers would’ve been gone by then. Still he didn’t. Why?