The Firm and Secure Gospel
Most of this letter was to rebuke and correct the wrong teaching and practice in the church at Corinth. They had been spiritually side-tracked, as demonstrated by their wrong behaviour. So Paul concluded the letter by encouraging them to refocus on the true gospel about Jesus, His death and resurrection. The faith of the church can never rest on Christian morals and doing good (Ephesians 2:8-9). It must rest on Jesus who died to pay for the punishment our sins deserve, and who was raised to make us right with God (Romans 4:25).