At least thirteen of the letters (epistles) in the New Testament were written by St. Paul. A fourteenth, the Letter to the Hebrews, is probable but not certain. These letters are addressed either to the Christians of various local communities or to individuals; the Canon of Scripture does not place them in chronological order. All of Paul’s letters reveal his tireless efforts to teach the Faith and build up the Christian community, especially in those places where he was the first to bring the Christian message.
"Stand firm and hold fast to the traditions that you were taught by us, whether by word of mouth or by our letter (2 Th 2:15)."