Quran (3:56) - "As to those who reject faith, I will punish them with terrible agony in this world and in the Hereafter, nor will they have anyone to help."

Quran (8:12) - "I will cast terror into the hearts of those who disbelieve. Therefore strike off their heads and strike off every fingertip of them"

 

Of course, there are some muslims who claimed that these were said as an instructions during the war or fight.  Then why were these found in the quran and isn't quran supposed to be a book from allah?  Then they were told not to simply interprent the quran otherwise they could become an apostat and the above verses are the punishment.  They were reminded if you interpret, you are challenging your allah!  What allah said and means only allah knows.  That really shut them off.