Pope Saint Leo the Great

Although the universal Church of God is constituted of distinct orders of members, still, in spite of the many parts of its holy body, the Church subsists as an integral whole, just as the Apostle says: “We are all one in Christ,” nor is anyone separated from the office of another in such a way that a lower group has no connection with the head. In the unity of faith and baptism, our community is then undivided. There is a common dignity as the apostle Peter says in these words: “And you are built up as living stones into spiritual houses, a holy priesthood, offering spiritual sacrifices which are acceptable to God through Jesus Christ.” And again: “But you are a chosen people, a royal priesthood, a holy nation, a people of election.” For all, regenerated in Christ, as made kings by the sign of the cross. They are consecrated priests by the oil of the Holy Spirit, so that beyond the special service of our ministry as priests, all spiritual and mature Christians know that they are a royal race and are sharers in the office of the priesthood. For what is more king-like than to find yourself ruler over your body after having surrendered your soul to God? And what is more priestly than to promise the Lord a pure conscience and to offer him in love unblemished victims on the altar of one’s heart? 

-- Pope Saint Leo the Great from a sermon