If someone claims
they know things that nobody else knows, like things that haven't happened yet
or secrets of the unseen, it's a big problem. According to Islam, they're
actually considered a disbeliever because they're saying something that goes against
what Allah has told us.
Allah, the Most High,
tells us in the Quran, "Say (O Messenger): None in the heavens and the
earth knows the Ghaib (unseen) except Allah, nor can they perceive when they
shall be resurrected." This means only Allah knows what's hidden and
what's going to happen in the future.
So, if someone says
they know these things, they're basically saying they know better than Allah or
even the Prophet Muhammad. That's not okay because Allah has chosen certain
people, like prophets, to tell us what we need to know. And even the Prophet
Muhammad himself said, "I do not claim that with me are the treasures of
Allah, nor do I know the unseen; nor do I say to you that I am an angel. I only
follow what is revealed to me."
In other words, if someone claims they know things that only Allah knows, they're going against the teachings of Islam. So, it's a serious matter.