God's Words are more than words. They are actions. 

When we say words, they may have emotional impact, but they don't have the power to act. If you have ever walked into a room and said, "let there be light," you have discovered that you still have something to do.

In the beginning God did not say, "Let there be light," and then make light.

His words have their own power. In the saying everything was created.

In chapter 4 of I Samuel we get to see God's Words acting upon a nation. The words He spoke to Samuel have their own power, and they never fall to the ground.