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.
Ephesians 1:19-23
"and what is the exceeding greatness of his power to us-ward who believe, according to the working of his mighty power, which he wrought in Christ, when he raised him from the dead, and set him at his own right hand in the heavenly places, far above all principality, and power, and might, and dominion, and every name that is named, not only in this world, but also in that which is to come: and hath put all things under his feet, and gave him to be the head over all things to the church, which is his body, the fulness of him that filleth all in all"