1 Corinthians 1-4
It was during Paul’s 2nd missionary journey that he went to Greece (Macedonia and Achaia) after receiving a vision of a man who begged him to come to that region. After founding fellowships in Philippi and Thesallonica, he lived and taught for almost 2 years in Corinth. However, after his departure, false teachers came in and corrupted the believers there, and when Paul heard of these things, he wrote this first epistle while he was in Asia Minor (Ephesus). The first 6 chapters deals with correction and discipline from Paul, and the rest of the book deals with doctrinal questions he had received from them.
The first issue Paul addressed was the problem of division that had cropped up in Corinth, where people in the church were arguing about which of the apostles was the most important. Groups within the church had formed, where some claimed Paul as their highest authority, others claimed to follow Apollos, others followed Peter, and even some said “I only follow Jesus”. Paul explains to them that none of the apostles are in competition, as they are all just servants of Jesus Christ, who is the head of the church. However, he also tells them that he was writing to bring correction, and he had earned that right to do so because he had been the instrument of their salvation - only he could be called their spiritual father.
Paul tells them to stop their arguments and disagreements of such foolish things, as spiritual divisions like these are just a tool of the devil to disrupt the work of the gospel to unbelievers.