As the rain and the snow
come down from heaven,
and do not return to it
without watering the earth
and making it bud and flourish,
so that it yields seed for the sower and bread for the eater,
so is My word that goes out from my mouth:
It will not return to Me empty,
but will accomplish what I desire
and achieve the purpose for which I sent it.
God's words have power.
The Hebrew word that we translate as "word" here is more than just what our Bibles say. It also speaks to words that God may speak to us.
These verses then remind us that God's word - both in Scripture and when He speaks to us through other ways - has power, purpose, and meaning.
When God speaks something, what he intends to happen because of those words will happen. These verse makes that pretty clear.
We can see how God's words had power over and over as we read Scripture. When God spoke and said that something would happen, it did. It starts with the creation account in Genesis where God spoke everything into being.
This means that when God speaks to us regarding something for our lives, what He has determined will happen. We have a choice in whether we cooperate with what God says, but what He says will happen.