Why did Paul have to constantly defend his apostleship to the Corinthians?
Paul had to defend his apostleship because the Corinthian church was divided by party loyalties. Some claimed Peter had authority since he walked with Jesus for three years, while Paul had not, and they dismissed Paul as a fake or imposter. Yet Christ had sent him as apostle to the Gentiles.
Les explains that the whole letter of Corinthians deals with a series of problems, including divisions, morality, and relationships within the church family. Some in the congregation separated themselves, saying they listened only to Peter, while others said they listened to Apollos. Because Peter had walked with Jesus for three years, Paul's opponents said Paul was a fake and an imposter, and that Peter was the one with authority. So Paul has to constantly defend his apostleship. He insists that he is judged of no man except Jesus Christ, the one who sent him out as the apostle of the Gentiles in the first place. Therefore, since no one can judge Paul except the Lord who sent him, believers should judge nothing before the time until the Lord comes.