Hebrews 12:25  See that ye refuse not him that speaketh. For if they escaped not who refused him that spake on earth, much more shall not we escape, if we turn away from him that speaketh from heaven:

26  Whose voice then shook the earth: but now he hath promised, saying, Yet once more I shake not the earth only, but also heaven.
27  And this word, Yet once more, signifieth the removing of those things that are shaken, as of things that are made, that those things which cannot be shaken may remain.
28  Wherefore we receiving a kingdom which cannot be moved, let us have grace, whereby we may serve God acceptably with reverence and godly fear:
 
God will shake, not only the earth, but also heaven!
 
He prophesied exactly that in Matthew 24:
 
Matthew 24:29  Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
30  And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
 
As stated above, God will shake, not only the earth, but also heaven, that only those things that cannot be shaken will remain.
 
What cannot be shaken?
The Kingdom that we will receive cannot be shaken (Hebrews 12:28).