[Originally preached on September 29, 444:]
So proclaims the most blessed apostle Peter when he says with these most sacred words: “And you yourselves should be built up like living stones into spiritual dwellings, a holy priesthood, offering spiritual sacrifices acceptable to God through Jesus Christ” (1 Pt. 2:5). And later on he says: “You, however, are a chosen race, a royal priesthood, a holy nation, a people set apart" (1 Pt. 2:9). All who have been regenerated in Christ are made kings by the sign of the cross and consecrated priests by the anointing of the Holy Spirit.
Apart from the particular service that our ministry entails, all Christians who live spiritual lives according to reason recognize that they have a part in the royal race and the priestly office. What could be more royal than the soul in subjection to God ruling over its own body? What could be more priestly than dedicating a pure conscience to the Lord and offering spotless sacrifices of devotion from the altar of the heart? Since this has been given to everyone alike through the grace of God, it is a devout and praiseworthy thing for you to take joy in the day of our elevation as if in your own honor. Let the episcopacy be celebrated in the entire body of the Church as one single mystery. When the oil of benediction has been poured out, the mystery flows, though more abundantly onto the higher parts, yet not ungenerously down to the lower ones as well.
---
Source: Pope St. Leo the Great, "Sermon 4," in Leo the Great: Sermons (The Fathers of the Church: A New Translation), trans. by Jane Patricia Freeland and Agnes Josephine Conway (Washington, DC: The Catholic University of America Press, 1996), 25–26.