In introducing himself to the Ephesians, Paul identifies himself as “an apostle of Christ Jesus by the will of God” (Ephesians 1:1). There are several points that need to be mentioned about this “title” that Paul gives to himself. Paul is saying that he did not appoint himself as an apostle, but that he was appointed to be an apostle by the will of God.
In the days of Paul, the word “apostle” was not necessarily a religious word. It could mean a delegate or a messenger, but added information had to be given to understand who this “apostle” was representing. In the New Testament, it applied to the twelve men Jesus appointed from among His followers to be His special delegates or messengers to the world. Paul, in other writings, claims to have the same authority as these original twelve men.