"Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand, and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain. For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures..."
~ 1 Corinthians 15:1-4
D.A. Carson makes four helpful observations concerning the Gospel (from For the Love of God)
First, “the Gospel” is not in the first instance about something God has done for me, but about something God has objectively done in history. It is about Jesus, especially about his death and resurrection. We have not preached the Gospel when we have told our testimony and no more, or when we have conveyed an array of nice stories about Jesus, but not reached the telos (the goal or end) of the story told in the four Gospels.
Second, the primary events of this Gospel unfolded “according to the Scriptures.” The precise way in which the Scriptures predicted these events—often by typology—is not our immediate concern; rather, it is the simple fact of the connection with Scripture that is so stunning. No one in the early church saw the significance of Jesus as something brand new, or standing in isolation from all that had come before. Rather, they saw him as the capstone, the culmination, the glorious goal, the climax of all of God’s antecedent revelation in holy Scripture.
Third, this Gospel saves us (1 Cor. 15:2). A great deal of theology is already presupposed by these few words: in particular, what we are saved from. Embedded here are Paul’s understanding of human beings made in the image of God, the awfulness of sin and the curse of God that has separated us from our Maker, our inability to make ourselves over. The Gospel saves us—and always we must bear in mind exactly what it is that we are saved from.
Fourth, Paul makes clear not only the object of this saving faith (namely, the Gospel), but also the nature of this faith: it is faith that perseveres, that holds firmly to the word preached by the apostles. “Otherwise, you have believed in vain” (1 Cor. 15:2)—a point often made in the New Testament (e.g., John 8:31; Col. 1:23; Heb. 3:14; 2 Pet. 1:10).