These are words with purpose. But there is more to the reading from Isaiah.
“My word shall not return to me void, but shall do my will,” sounds almost as if the word itself is taking action. That is, this unusual description makes it seem like the word is a living thing sent by God.
This may be an odd turn of phrase, but it is also an intentional turn of phrase. The image of the word taking action is part of Isaiah’s message as well.
One of the Gospels (John) also sees the word as taking action, and identifies the word. The word is also The Word. Which means that it should be no surprise that God’s words are fulfilled by The Word. More on this tomorrow.