@ Martin
First logically speaking God can never show himself to anyone in the chessboard unless he do it in the form of something IN the chessboard itself (unless he want to brake the rules of the chessboard he created and he WILL one day
).
God translated Quran to Mohammed through an Angel named (جبريل
piece by piece, Quran pretty much summed everything God wanted to explain to humanity (ethics, principles, moral, rules....).
This is what he did, as short as possible.