Paul is addressing the believers in Corinth, reminding them of the centrality of the gospel message for their salvation. The gospel, which includes the death, burial, and resurrection of Jesus Christ, is the foundation of Christian faith. Paul stresses that salvation is not just a one-time event but a continuous process that requires believers to remain steadfast in their faith. Holding firmly to the word preached means actively living out the teachings of Jesus and maintaining a strong, unwavering faith. This is crucial because without perseverance, the initial belief might not lead to the intended spiritual transformation.
The phrase 'believed in vain' serves as a caution against complacency. It suggests that faith without ongoing commitment and action may not yield the fullness of salvation. This message encourages believers to examine their faith, ensuring it is active and alive, characterized by a deep, enduring relationship with God. Paul’s words serve as both encouragement and warning, urging believers to remain committed to the gospel throughout their lives.