I thought there are some 'proofs', by people that have an experience with Allah. Couldn't find one of those! What is strange is that one proof is, that Allah proofs himself, by saying that he's proofed! (Sounds weird but follows the principle that you can't explain a word with the word itself!).
This differs from my christian religion. This is shall be no offense, I just put my thoughts here! In our religion, people can tell about experience they made personally in having a relationship to god. That is something that is missing in my opinion. I don't say that this is bad, I just compare to the religion I know!