'Empty' in the Bible

Even Egypt, whose help is vain and empty.Therefore, I have called her“Rahab who has been exterminated.”

I say, ‘Your counsel and strength for the war are only empty words.’ Now on whom do you rely, that you have rebelled against me?

So will My word be which goes forth from My mouth;It will not return to Me empty,Without accomplishing what I desire,And without succeeding in the matter for which I sent it.