Is the prayer valid behind one who claims knowledge of the unseen?

The questioner : Some people build houses in the air and perform i'tikaf (spiritual retreat) in them, and when they come out, they report news of the unseen, saying that such and such will happen at such and such a time.

The Shaykh : They build in the air, meaning in the sky.

The questioner : From outside.

The Shaykh : Yes, because when you said "af" and then "qatal" (killed), and then said "leave me alone regarding knowledge of the unseen," you thought he was a listener to the jinn.

The questioner : Are these people among you?

The Shaykh : No, the one who claims knowledge of the unseen is a disbeliever. Every person who claims knowledge of the unseen is a disbeliever. And if one goes to a fortune-teller and believes what he claims of knowledge of the unseen, he has disbelieved in what was revealed to Muhammad. What about the fortune-teller himself? No, and it is not permissible. And this exists in the lands, glory be to Allah. Yes.