1 Corinthians 15:14

Preaching. Gr. kerugma, “the thing preached.” The emphasis is on the content of the preaching (see on ch. 1:21).

Vain. Gr. kenos, “empty,” “without content,” “devoid of truth” (cf. on v. 17), an apt description of any attempt to preach the gospel apart from the resurrection of Jesus. Such preaching would indeed be “empty,” robbed of one of its central, historical facts. If Christ be not risen, Christian witness is condemned on two counts: (1) Jesus repeatedly declared that he would rise from the dead (see Matt. 16:21; 17:22, 23; 20:17-19; etc.), and if He did not rise, He was an impostor; (2) the apostles were basing their preaching on an event that they alleged did occur, and thus were parties to the imposture, holding out a hope that could not be fulfilled.

Your faith. Disbelief in the resurrection invalidates not only apostolic preaching but also Christian belief in that preaching. By doubting the possibility of a resurrection, such men were destroying all they had previously held dear.