Answer
When the New Testament speaks of the gospel, or the "good news," it's evoking imagery from the book of Isaiah, especially Isaiah 52:7, because in the context of that, God is promising to restore his people. And so he says how blessed is the one the feet of those who bring good news to Zion, good news of peace, announcing , "Your God reigns." So, in the New Testament we read about the good news of peace, we read about the good news of God's reign, God's kingdom, and what that evokes is the promise that God is going to restore his people and bring salvation.
Answer by Dr. Craig S. Keener
Dr. Craig S. Keener is the F.M. and Ada Thompson Chair of Biblical Studies at Asbury Theological Seminary.