A quote from the book Preaching The Cross p.19. I think it’s a good illustration.

Why does the postal service exist? Why do we pay mailmen to do? Do we pay them to write letters to us and put them in our mailboxes? No. We pay them to deliver faithfully the message of someone else. The mailman has been entrusted with other people’s messages to us. The same is true with ministers and their ministries. We are not to invent the message but to faithfully deliver God’s message to his people. That is our calling, which means that we are called as ministers only insofar as we present God’s message to his people. It is God who owns the church, and it is by his Word that he creates his people. -Mark E.Dever