It was penned by St Ignatius of Antioch to the Ephesians just at the beginning of the second century. Bishop Ignatius was on his way to Rome and facing certain martyrdom. Travelling across across Asia Minor from Antioch, he stopped and met with the pastoral leadership of various churches.
These and Ignatius' other letters show the level of organization already existing in the Church just after the death of the last Apostle, John.
Saint Ignatius of Antioch (? – around 110), bishop and martyr From the Letter to the Ephesians (translation breviary)
"It is right for you to give glory in every way to Jesus Christ, who has given glory to you; you must be made holy in all things by being united in perfect obedience, in submission to the bishop and the presbyters. I am not giving you orders as if I were a person of importance. Even if I am a prisoner for the name of Christ, I am not yet made perfect in Jesus Christ. I am now beginning to be a disciple and I am speaking to you as my fellow-disciples.
It is you who should be strengthening me by your faith, your encouragement, your patience, your serenity. But since love will not allow me to be silent about you, I am taking the opportunity to urge you to be united in conformity with the mind of God.
For Jesus Christ, our life, without whom we cannot live, is the mind of the Father, just as the bishops, appointed over the whole earth, are in conformity with the mind of Jesus Christ. It is fitting, therefore, that you should be in agreement with the mind of the bishop as in fact you are.
Your excellent presbyters, who are a credit to God, are as suited to the bishop as strings to a harp. So in your harmony of mind and heart the song you sing is Jesus Christ. Every one of you should form a choir, so that, in harmony of sound througt harmony of hearts, and in unity taking the note from God, you may sing with one voice through Jesus Christ to the Father... It is then an advantge to you to live in perfect unity, so that all times you may share in God."