In "God's Word for Today" David Woods writes:
We have all witnessed the power of the spoken word, power to encourage and strengthen a person who is dis-couraged or cowed by intimidating life challenges as well as the power to destroy the confidence and self-image of someone desperately needing affirmation. We have also seen the impotency of speech to stop the rebellious child from pursuing a wrong path or inability of a sincere entreaty to soothe a vengeful spirit. But none of us have witnessed the creation of galaxies by mere words.
Source: Studies in the Psalms: Adult Teacher's Insights, page 30.