Yesterday and today in the liturgy we get two popes in row, yesterday having been the optional memorial of Pope Blessed Gregory X and today the obligatory memorial of Pope St. Agatho. Not knowing if there are proper readings for their Offices of Readings and not knowing anyway where to look for them if they did indeed exist, this led to me praying over the same second reading two days in a row, a passage from the sermons of that mainstay of the breviary, Pope St. Leo the Great, which the Liturgy of the Hours provides for popes in the Common of Pastors.
At the end Pope Leo provides a wonderful definition of Petrine primacy:
In universa namque Ecclesia, Tu es Christus, Filius Dei vivi, cotidie Petrus dicit, et omnis lingua, quae confitetur Dominum, magisterio huius vocis imbuitur.
In the whole Church, Peter says each day, You are the Christ, the Son of the living God, and every tongue which confesses the Lord is dipped in the magisterium of his voice.