We talk about the gospel as an announcement—a promise—that is revealed as a grand drama that unfolds from Genesis 3:15 to the close of Revelation. The gospel isn’t an offer to appropriate, decide, or contract for with Jesus. It’s an announcement—a declaration—of God’s saving accomplishment in Jesus Christ. Promised in the Old Testament, the gospel is fulfilled in the New. The call to repent and believe is not the gospel, but the proper response to the gospel. In fact, the gospel is not a call to do anything—even to believe. The gospel itself is simply an announcement that we are therefore called to believe.
– by Mike Horton in a book review found here