In the first century A.D., Clement of Rome, a direct disciple of the apostles, wrote in his letter to the Corinthians:
"The apostles have preached the Gospel to us from the Lord Jesus Christ; Jesus Christ [has done so] from God. Christ therefore was sent forth by God, and the apostles by Christ. Both these appointments, then, were made in an orderly way, according to the will of God. Having therefore received their orders, and being fully assured by the resurrection of our Lord Jesus Christ, and established in the word of God, with full assurance of the Holy Ghost, they went forth proclaiming the kingdom of God was at hand."
If we examine the first 1,500 years of Church history, we discover that while some came awfully close to redefining the Gospel, no one actually did. In fact, in the thirteenth Century, Thomas Aquinas wrote:
"Since Christ said at the very outset of the preaching of the Gospel: 'the kingdom of heaven is at hand' (Matt. 4:17) [sic], it is most absurd to say that the Gospel of Christ is not the Gospel of the kingdom."
It is not until we reach the Reformation where the Gospel is redefined in light of the atonement. Who is the culprit of this grave error? None other than Martin Luther. Luther's redefinition of the Gospel first appeared in print in May of 1520 in "A Treatise on Good Works," where he wrote:
"It must, therefore, be a grievous sin not to hear the Gospel, and to despise so rich a treasure and so rich a feast to which we are bidden, but a much greater sin not to preach the Gospel, and to let so many people who would gladly hear it perish, since Christ has so strictly commanded that the Gospel and this testament be preached, that He does not wish even the mass to be celebrated, unless the Gospel be preached, as He says, 'As oft as ye do this, remember Me'; that is, as st. Paul says, 'Ye shall preach of His death.' [1 Cor. 11:26]"
In August of the same year, he wrote in "A Treatise on the New Testament That is the Holy Mass":
"What is the whole Gospel but an explanation of this testament? Christ has comprehended the whole gospel in a short summary with the words of this testament or sacrament. For the whole Gospel is nothing but a proclamation of God's grace and of the forgiveness of all sins, granted us through the sufferings of Christ, as St. Paul proves in Romans X [Rom. 10:9, 11, 13]; and Christ in Luke XXIV [Luke 24:46-47]."
Luther's agony over the justice of God led him not only into embracing "justification by faith" but also in redefining justification by faith as "the gospel." I believe in justification by faith, but it is not the Gospel. Romans 10 does not mention the suffering of the King, nor does it "prove" the gospel is grace and forgiveness through the King's suffering. Romans 10:9-13 offers salvation only to those who "confess with your mouth Jesus is Lord and believe in your heart God raised Him from the dead."
Luke 24 does not "prove" the atonement was the gospel either. The word "gospel" does not even appear in this chapter. Why did Luther not reference Luke 16:16 where Jesus used the word "gospel" and explicitly defined it as "the Kingdom of God"? Like most people today, Luther looked for proof text to support his logical leap.
No one in Scripture or outside of Scripture ever called the atonement "gospel" until Martin Luther. The sharpest mind of the Reformation period, Desiderius Erasmus, caught Martin Luther in his gospel crime. In typical Luther fashion, he insulted and attacked Erasmus with vehemence and crassness, calling Erasmus a liar, a blasphemer, and a closet atheist, deeming his words to be feces or dung served for consumption on gold and silver plates. Erasmus chided Luther for his logic and his unscholarly and unspiritual insults, claiming that any theologian who would dare break from all tradition should be a man of exceptional character, not of crass insults. (Erasmus strongly protested the corruption in the Catholic hierarchy and sought to reform the institutions from within the system.)
While the Reformation sought to improve the corruptions of the Catholic institution, nevertheless they introduced their own grave errors. For example, Luther embraced the teachings of the Gnostics, that "there can be no such thing as free will." (See the first three centuries of Christians for their beliefs on free will.) The Reformers sought to improve the existing institution, which was the Catholic system. Their grave error here was in not seeking to restore the apostolic traditions and practices. Instead, they sought to retain certain elements of the existing institution while reforming only certain elements. A lot of their reform that resulted in errors just as corrupt and grave as that of the Catholics was due to their use of proof text methodology. From the time of the Reformation onward, Christians have divided into hundreds of different denominations all based on their own particular proof text methodology. From the time of the Renaissance onward, Christians have become selfish and individualistic in their thinking and behaviour, leading them to many grave errors in assumptions imposed upon Scripture.
The atonement is not the Gospel! Period. Those who preach otherwise demonstrate their own ignorance and lack of legitimate education (which does not come from a Semitary—er, I mean, Seminary). Without a first-century model, and without understanding historical-cultural background, you will necessarily and inevitably misinterpret Scripture, as most preachers do today. They may have good intentions, but their intentions are ignorant.
Instead of supplanting the message Jesus and His apostles explicitly called "Gospel," we should inquire how repentance and forgiveness of sins are part of the message Scripture explicitly calls "Gospel": the Good News of the Kingdom of God.
Jesus is King, Yahweh's Anointed, and the Kingdom of God has come near. Die to yourself, give up your right to yourself, and submit yourself to the rule of Jesus over your life. Then you shall have salvation! That is the Gospel! If Jesus is not your King, the ruler of this world is your ruler, and your sin (for which you believe Jesus died) still governs you! Repent today!