Please read the passage before reading the commentary
If there is no resurrection from the dead, then death is the complete ending of our life and all that is left after death is nothingness.
If there is no resurrection from the dead, then that applies to Christ as well as to us. If no one rises from the dead, then after death, there is no resurrection even for Christ. If Christ has not risen from the dead, then there is no respite from our sins. If Christ has died for our sins, then he is dead and so are we, but this means that that there is no redemption from our sins. It takes the death and the resurrection from the dead, not just the death, for Christ to give us his new life. Without his resurrection Christ could not give us new life; he could only give us his death and we would still be dead, not alive.
If there is no resurrection from the dead, then our ancestors have lived a lie and we have bought into that lie. Living a lie is not living life; it is being dead. The ancient creed quotes from this fifteenth chapter (15:3-4) to proclaim that Jesus has died, was buried, and rose from the dead according to the Scriptures. The burial asserts that Jesus died because we only bury dead people.
Based on God’s word of truth, according to the Scriptures, Christ, was buried and rose from the dead. This whole divine process of death and resurrection is our hope. God associated Godself into our lives by taking on human nature. In that human nature, Christ became a second Adam and died once for all of us so that he could rise again, once for all of us, so that could rise with him. This is what Paul says he had learned from God and faithfully passed on to us.
Therefore, since Christ died and rose from the dead in our human nature, we likewise are destined to rise form the dead as he has. Therefore, dead does not end our existence, but allows us to continue living beyond death, with Christ in his glory. Christ, raised from the dead, is now the firstfruits of all who have fallen asleep, including us who will eventually fall asleep.