What will confront man after death? What will become of him in the grave? How will he rise again on the Day of Judgement? These, are those states of affairs, which we have not yet witnessed. But Allah Taala has made all these circumstances clear to us, in great detail, through his Messengers alaihimus salaam and lastly through the Holy Prophet Muhammad sallallahu alayhi wasallam who is the Seal of Prophethood.
There are many authentic hadiths that prove the existence of the punishment and the bliss in the grave to whoever deserves them, and also the questioning of the two angels in the grave.