thoughts and ruminations while in exile (1 Pet. 2:11)

Don Carson gives a nice summary of the gospel here:

The heart of the gospel is what God has done in Jesus, supremely in his death and resurrection. Period. It is not personal testimony about our repentance; it is not a few words about our faith response; it is not obedience; it is not the cultural mandate or any other mandate. Repentance, faith, and obedience are of course essential, and must be rightly related in the light of Scripture, but they are not the good news. The gospel is the good news about what God has done. Because of what God has done in Christ Jesus, the gospel necessarily includes the good that has been secured by Christ and his cross work. Thus it has a present and an eschatological dimension. We announce the gospel. (pp. 160-162)

This is taken from his essay, "What is the Gospel?--Revisted," in For the Fame of God's Name: Essays in Honor of John Piper., eds. Sam Storms and Justin Taylor (Wheaton: Crossway, 2010).