The fifth of Paul's Epistles, and the tenth book in the New Testament, is Ephesians. It was written some time around 61 AD whilst Paul was a prisoner in Rome, awaiting his trial by the Emperor Nero; a persecutor of Christians.
Paul's letter to the Church at Ephesus (in modern day Turkey) is not an admonishment, like some of his other letters, but rather an encouragement. Paul describes the nature of the Church as a living thing; the body of Christ. He then tells the Ephesians to act like Christ's body on earth.