The apostle came first to Corinth preaching the gospel and many were saved. The second time he was hindered in coming because of conditions in the assembly which needed discipline. Now the third time he was coming. The testimony of some would be tried by two or three witnesses.
Paul says that if Christ had not spoken by him, Christ did not dwell in them. If Christ was in them, Christ must have spoken by Paul. He was the means of their salvation.
"Examine yourselves, whether ye be in the faith." They were to examine themselves to see how they came into the faith. Was it through the apostle? If so, then Paul was an apostle. The apostle had opened his heart to the Corinthians and had written to them what the Spirit had caused him to say. He wrote, being absent so they could weigh his words, and so when he came, there would be a changed attitude toward him.
He closed the epistle with words of comfort and an exhortation to be of one mind and to live in peace, desiring that the God of love and peace be with them.