This speaks of the power of God and the sure and eventual completion of the plans He has.  As is stated in Isaiah 55:10-11, “For as the rain and the snow come down from heaven, and do not return there without watering the earth and making it bear and sprout, and furnishing seed to the sower and bread to the eater; 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.”