Summary: Those who deny the truth of the resurrection are teaching a different gospel to that which we find in the New Testament.
I BELIEVE IN THE RESURRECTION
Sometimes it is necessary for Christian people to get back to the basics of their faith, to remind themselves what they are about. Here in 1 Corinthians, Paul is not teaching his readers something new, but reviewing that which he taught them from the very beginning (1 Corinthians 15:1). Perhaps now, as much as at any other time, the Church needs to remind herself of the fundamental truths of the gospel.
Despite the fact that the Corinthians had earlier embraced Paul's teaching, the Apostle was aware that other influences were disturbing their peace. There were even some amongst them who denied the fact of resurrection (1 Corinthians 15:12). Perhaps the Corinthians were keeping company with some Sadducees, who denied the resurrection (Luke 20:27); or perhaps with some Greek philosophers, who doubted it (Acts 17:32).
Without approving of the custom, Paul mentioned those who are baptised for the dead, indicating that “they” had the sense to know that there is a resurrection (1 Corinthians 15:29). Ultimately the element of doubt comes from outside the church, which is why Paul unashamedly quotes a warning (from a pagan source) about the company we keep (1 Corinthians 15:33). The fact of the matter is that a denial of the resurrection is both a cause and a symptom of spiritual and moral bankruptcy.
Paul does not deny that the majority of the congregation are still standing in the truth (1 Corinthians 15:1), but he still exhorts them to “hold fast” (1 Corinthians 15:2). We need to reiterate, from time to time: “This is the faith of the Church. This is our faith, and so we believe and trust.”
The gospel which Paul preached was no different from that of the other Apostles, nor was it any different from that which the Church had received. The good news is that Christ has died (1 Corinthians 15:3), Christ is risen (1 Corinthians 15:4), and that Christ will come again (1 Corinthians 15:23). All this was in fulfilment of the Scriptures.
The death of Jesus is foreseen in Psalm 22 and Isaiah 53. His resurrection is foretold in Psalm 16:10, and in the typological accounts of Abraham and Isaac (Genesis 22), and Jonah and the big fish. Our resurrection upon the Lord's return is anticipated in Job 19:25-27.
The evidence in favour of Jesus' resurrection is overwhelming. He was seen by Peter and “the twelve”; by five hundred of His followers at once (most of whom were still living when Paul wrote, and others who had “fallen asleep” and were no doubt awaiting their own resurrection); by James the brother of Jesus (who no doubt needed some convincing); then by the apostles again; and then by Paul himself “as one born out of due time” (1 Corinthians 15:5-8). In any court of law a matter is established by two or three witnesses, but some of these people had not even believed it themselves, but now were willing to suffer for the truth of it (1 Corinthians 15:30).