The word 'gospel' means 'good news'. The good news of Jesus Christ is the most important matter there is to know, for by it we are saved from sin and death and being lost to God - providing we keep holding on to the good news without diluting it. What exactly must we believe? Paul goes on to say.
The first thing is that Christ died for our sins according to the Scriptures. No-one in his day disputed that Jesus had died. It is the reason for his death that is so important: he died for our sins. That is what the Scriptures bear witness to - see Isaiah 53:4-6 for example. Remember that Jesus is the Son of God, through whom and for whom everything had been made (Colossians 1:16). Yet he left the glory of heaven, and became a human being, and submitted to the most cruel death of crucifixion - for our sakes. The greatest suffering was not the physical pain, but the ultimate death of separation from God (Mark 15:34). By his suffering and death Jesus Christ removed the road block that our sins have placed between us and God, making it possible for us to be forgiven and accepted and loved by God, here and now.
Equally important is what happened next: he was buried, and raised to life again after three days, according to the Scriptures. The early church quoted Psalm 16:10 (decay set in after three days normally, see John 11:39). But Paul did not stop there: while Scripture was the most important evidence, there were also many eyewitness to Jesus' resurrection, including 500 at one time. (The letter to the Corinthians was written before any of the four Gospels, so this is the earliest account of the resurrection we have.) This was no 'spiritual resurrection'; it was a physical resurrection of the body, and Paul says that unless we believe that, our faith is in vain (v.2). Paul was not interested in a purely spiritual after-life; he was looking forward to a new creation, better than this one, and it would not be better if it was not at least as solid! Jesus makes the same point: he was no ghost, but real flesh and bones, Luke 24:39. Our hope for an eternal, better, future is based on the physical resurrection of Jesus.
Such good news cannot be kept to ourselves. Paul had received it; he saw it was good news of God's great grace, which could reach even him (v.10); and he passed it on. We too have received it; we too need to pass it on.
ISSUES AND QUESTIONS
Why are these things so important? Why shouldn't we keep this good news to ourselves?
IDEAS FOR MEETINGS
Welcome question: Can you tell us of a piece of good news that you could not keep to yourself, but had to pass on?
Worship: Sing or listen to an Easter song. Then ask the members of the group to imagine that they are one of the disciples in the upper room on that first Easter Sunday. Tell the story of Luke 24:33-49, with plenty of pauses to enable people to enter imaginatively into the scene. End with a song such as 'I, the Lord of sea and sky' (whom shall I send?).