I Cor. 1:1-9
Paul did not have access to forms of instant communication, but he did receive news from the churches. The news from the church at Corinth disturbed him. The Holy Spirit guided him to write a letter while he was in Ephesus to correct the problems that were in the Corinthian church.
As previously stated, the people of Corinth were highly immoral. The church was made up of this class of individuals who had been converted from their idolatry, prostitution and general immoral behavior. It became necessary for Paul to remind them that they were to refrain from returning to this way of life.
Paul identified himself as an apostle in order to emphasize his authority. He addressed the church as saints who were set apart in Christ and called by the preaching of the gospel. The first part of the letter complemented the Corinthians by pointing out their spiritual relationship with the Lord Jesus Christ.