In one sense, the whole Bible is the gospel. Reading it from Genesis to Revelation, we see the vast sweep of God's wonderful message to mankind.
But many people read the whole Bible, and their understandings of the gospel differ widely, remain vague, or are just plain wrong. Some speak of the gospel in terms of God's favor pouring out in financial prosperity. Others describe a political utopia in Christ's name. Still others emphasize following Christ, bringing in His kingdom, or pursuing holiness. Some of these themes are biblical. But none of them is the gospel.
Fortunately, we can turn to passages that tell us, explicitly and clearly, what the gospel is. For example, the Apostle Paul explains what is "of first importance" within the biblical message:
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 Cor. 15:1-4)
Paul reminds the Corinthian believers of the gospel message and its comprehensive relevance to them. They received it, they stand in it, they are being saved by it. These sacred and powerful benefits flow into their experience as they hold fast to the gospel word that Paul gave them. The Corinthians do not deserve such blessing, but the gospel announces God's grace in Christ for the undeserving. The Corinthians' only catastrophic failure would be unbelief. With so much to commend about the gospel, no wonder Paul ranks it as "of first importance" in his priorities.
What, then, is the gospel? The gospel is the good news from God, first, that "Christ died for our sins." The Bible says that God created Adam without sin, fit to rule over a good creation (Gen. 1). Then Adam broke from God and brought our whole race down with him into guilt, misery, and eternal ruin (chap. 3). But God, in His great love for us rebels now thoroughly unfit for Him, sent a better Adam, who lived the perfect life we've never lived and died the guilty death we don't want to die. "Christ died for our sins" in the sense that, on the cross, He atoned for the crimes we have committed against God our King. Jesus, dying as our substitute, absorbed into Himself all the wrath of God against the real moral guilt of His people. He left no debt unpaid. He Himself said, "It is finished" (John 19:30). And we will forever say, "Worthy is the Lamb who was slain!" (Rev. 5:12).
Second, the gospel says, "he was buried," emphasizing that the sufferings and death of Jesus were utterly real, extreme, and final. The Bible says, "So they went and made the tomb secure by sealing the stone and setting a guard" (Matt. 27:66). After killing Him, His enemies made sure everyone would know Jesus was stone dead. Not only was our Lord's death as final as death can be, it was also humiliating: "And they made his grave with the wicked" (Isa. 53:9). In His astonishing love, Jesus identified with us sinners and sufferers fully, omitting nothing.
Third, the gospel says, "he was raised on the third day." Years ago, I heard S. Lewis Johnson put it this way: the resurrection is God's "Amen!" to Christ's "It is finished." Jesus "was raised because of our justification" (Rom. 4:25 NASB). His work on the cross succeeded in atoning for our sins, and obviously so. Moreover, by His resurrection, Christ was "declared to be the Son of God in power"—that is, our triumphant Messiah who will rule forever (Rom. 1:4). The risen Christ alone can and does say to us, "Fear not, for I am the first and the last, and the living one. I died, and behold I am alive forevermore, and I have the keys of Death and Hades" (Rev. 1:17-18). The Living One conquered death and is now preparing a place for us—a new heavens and new earth, where all of His people will live joyously with Him forever.
This is the gospel of God's massive grace toward us sinners. Whatever else might be said only tells us more of the mighty work of Jesus Christ. Let us hold fast to the Word preached to us. If we believe this gospel, we cannot believe in vain.