Paul begins with his name and title, "an apostle of Christ Jesus." This is the same title Paul uses for himself in the first verses of 1 Corinthians, 2 Corinthians, Ephesians, 1 Timothy, and 2 Timothy. Paul was an apostle through the work and plan of God, not his schemes. The idea of God's will over his life is one of Paul's common themes in his letters. This not only gives Paul the authority to make his claims but also gives him reasons to endure persecution and suffering.
Paul wrote this letter along with Timothy, his longtime helper. Timothy is also listed as co-author with Paul in 2 Corinthians, Philippians, 1 Thessalonians, 2 Thessalonians, and Philemon. This makes Timothy a collaborator on six of Paul's 13 New Testament letters. Paul makes special mention of two other "brothers" in his letters. These are Apollos (1 Corinthians 16:12) and Titus (2 Corinthians 8:16).