1 Corinthians 1:1 - Joseph Benson’s Commentary on the Old and New Testaments

Paul, called to be an apostle There is great propriety in every clause of the salutation, particularly in this, as there was a faction at this time in the church at Corinth, which pretended to entertain doubts of his apostleship, 1 Corinthians 9:1; probably in consequence of insinuations thrown out against it by the Judaizing teacher, or teachers, who had come thither after his departure. The apostle, therefore, begins his letter by informing them, “that he was not, like Matthias, an apostle made by men, neither did he assume the office by his own authority, but he was called to it by Christ himself, who for that purpose appeared to him from heaven.” The original expression, κλητος αποστολος Ιησου Χριστου, is literally, a called apostle of Jesus Christ, or Jesus Christ's called apostle. Through the will of God Termed the commandment of God, 1 Timothy 1:1. This was, to the churches, the ground of his authority; to Paul himself, of an humble and ready mind. By the mention of God, the authority of man is excluded, Galatians 1:1; by the mention of the will of God, the merit of Paul, 1 Corinthians 15:8, &c. And Sosthenes If, as most commentators think, this person be that chief ruler of the synagogue at Corinth, mentioned Acts 18:17, as active in persecuting Paul, we must suppose that he was afterward converted, and became an eminent preacher of the gospel. And as it seems he had considerable influence among the Corinthians, it was prudence, as well as humility, in the apostle, thus to join his name with his own, in an epistle where he was to reprove so many irregularities. Sosthenes our brother Probably this word is emphatical; as if he had said, Who, from a Jewish opposer of the gospel, became a faithful brother.