From the Letter to the Ephesians by Saint Ignatius of Antioch, bishop and martyr, written some time before AD 117:
The harmony of unity
"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 through harmony of hearts, and in unity taking the note from God, you may sing with one voice through Jesus Christ to the Father. If you do this, he will listen to you and see from your good works that you are members of his Son. It is then an advantage to you to live in perfect unity, so that at all times you may share in God.
"If in a short space of time I have become so close a friend of your bishop – in a friendship not based on nature but on spiritual grounds – how much more blessed do I judge you to be, for you are as united with him as the Church is to Jesus Christ, and Jesus Christ to the Father, so that all things are in harmony through unity. Let no one make any mistake: unless a person is within the sanctuary, he is deprived of God’s bread. For if the prayer of one or two has such power, how much more has the prayer of the bishop and the whole Church."