From a sermon by Saint Augustine

This day has been consecrated for us by the martyrdom of the blessed apostles Peter and Paul. It is not some obscure martyrs we are talking about. Their sound has gone out into all the earth, and their words to the ends of the world. These martyrs had seen what they proclaimed, they pursued justice by confessing the truth, by dying for the truth.

So this is the reason for Peter’s acknowledged pre-eminence, that he stood for the Church’s universality and unity, when he was told, To you I am entrusting, what has in fact been entrusted to all. To show you that it is the Church which has received the keys of the kingdom of heaven, listen to what the Lord says in another place to all his apostles: Receive the Holy Spirit; and immediately afterwards, Whose sins you forgive, they will be forgiven them; whose sins you retain, they will be retained.

There is one day for the passion of two apostles. But these two also were as one; although they suffered on different days, they were as one. Peter went first, Paul followed. We are celebrating a feast day, consecrated for us by the blood of the apostles. Let us love their faith, their lives, their labours, their sufferings, their confession of faith, their preaching.