“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.” (1 Corinthians 15:1-2 ESV)
The Corinthian believers erred when they thought they had achieved spiritual perfection. One of the ways this manifested itself was in the widespread teaching that there was no bodily resurrection from the dead because they were already in their glorified state. Their bodies they deemed expendable and useless for the resurrection were spiritual not physical. This disdain for the body expressed as either ignoring it or by indulging its sinful cravings. So Paul reminded them of their common belief in the resurrection of Christ.
Paul’s teaching to the Corinthians serves to underscore one of the central truths of the Christian Faith: the belief in the literal bodily resurrection of Christ from the dead. It is one of those truth we affirm in the Apostle’s Creed. What Paul teaches indicates that if we deny Christ’s resurrection, if we say it never happened, then we are denying our own resurrection. Christ rose from the dead and this is the proof that He died for our sins. To deny this truth then means that we are still spiritually dead and incapable of pleasing God. Christ’s bodily resurrection is the ultimate proof that He defeated sin and death on the cross. Believers need not fear death because we are certain we will be raised again to eternal glory for we are united with Christ.