"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
What is sin? Sin is wrongdoing. It is the transgressing of a law; the breaking of a commandment. To be in a state of sin, which this verse says all of us are in, is to be in a state of guilt. Not just feeling guilty, which we may or may not, but in possession of real, objective, guilt. That is the state every human being is under. We have broken God’s law and, barring some kind of intervention, stand to receive the consequence of that law-breaking, which is death and punishment.
The Bible reveals that the only path to pardon for sin is forgiveness from the one sinned against. We might sometimes hear people talking about the importance of self-forgiveness and "leting go of the past." Yet there is every evidence to suggest that we don't really struggle to forgive ourselves. Rather, we are usually quick to give ourselves the benefit of the doubt and justify our wrong behavior. This might also explain why self-forgiveness does nothing to alleviate the weight of guilt.
The main issue is not whether we can forgive our own sins -- or even whether we can forgive each other’s sins -- but whether the Creator God, whose law we have broken, is the kind of God who forgives sins. If you're driving in the car with someone and they run a red light and get pulled over by the police, how impressed is that officer going to be if you lean over and say, “It’s okay officer, he was distracted but I’ve already forgiven him so don’t worry about a fine." Not very impressed. Why? Because though the driver may have sinned against you by putting you at risk, his real sin is against the Highway Traffic Act. It is a sin against a greater law.
As God is the ultimate authority, he is ultimately the one we have all sinned against. Therefore, he alone has the right to absolve or condemn us. We must also remember that the nature of sin is that it can just be waved away. For God to adopt the posture of a kindly grandfather, telling us sin is no big deal and we should just move on, would be to render him unjust. Sin is a crime against righteousness and in the Bible we see that "without the shedding of blood, there is no forgiveness of sins." The animals that were sacrificed as part of the old covenant system were to remind the Israelites that sin is costly; but they were only examples. Not only were animals unable to fully deal with the debt of sin, but they also failed to fully illustrate the full extent of God’s love and mercy, which is shown most clearly at the cross. In his death, Jesus pays the cost of sin; in his resurrection, he triumphs over death and secures all who trust in him.
This is the Gospel. This is God's Good News to sinners. But the implications of this Gospel stretch far beyond a narrow definition or a private experience. If Jesus really is the King -- if he really is the Savior of all men -- this is a reality that has far-reaching impact on the world. The claim is often made that only a narrow set of doctrines (the trinity, the atonement) qualify as “Gospel-centered” and are, therefore, the only ones that really matter. Yet all Scripture is breathed out by God and is “profitable for doctrine” (2 Tim. 3:16). And all doctrine has implications for the Christian life
The Gospel, therefore, starts with a confession. From there, it spreads to the whole man, and out into the whole of life.