For as the rain and the snow come down from heaven and do not return there without watering the earth ... so shall My word be which goes forth from My mouth
We know that everything basically living needs water to survive, be it plant, animal or human. Hydration is vital. We have found no sign of life without water. And this water graciously comes down from heaven above by the Creator's gracious command to accomplish the purpose for which He sends it: "watering the earth, and making it bear and sprout, and furnishing seed to the sower and bread to the eater." (verse 10)
This is beautiful, real picture of what the Word of God does also! It comes down from heaven above and does not return 'without' accomplishing the purpose for which He sends it: to create faith, to make it grow and sprout.
And what primarily does this Word of God accomplish? God answers in verse 7: "Let the wicked forsake his way, and the unrighteous man his thoughts; and let him return to the Lord, and He will have compassion on him; and to our God, for He will abundantly pardon." This is none other than the constant theme of the entire Bible: repent for your sins and believe that Jesus came do live the perfect life for you, be crucified, dead and buried and rise again for your forgiveness.
Does this make since to our natural way of thinking about us and God? No, for our thoughts are not God's thoughts, our ways are not God's ways! (verse 8-9) So, let God change your thoughts and ways to His Way and Truth: Jesus! (John 14:6) His Word changes our thoughts and ways to His, and they do accomplish the purpose for which He sends it: to forgive our sins for Christ Jesus' sake.
Repent and believe in the Gospel of Jesus Christ!