A reflection from The Liturgical Year, about today's epistle from Chapter 12 of the Acts of the Apostles, and which documents Peter's arrest and miraculous deliverance from prison:
It would be difficult to insist more than does to-day's liturgy on the episode of Peter's captivity in Jerusalem. Several antiphons and all the capitula of this Office are drawn from thence; the Introit has just sung the same; and the Epistle gives in full the history of the event in which the Church is particularly interested on this feast. The secret of her preference can easily be divined. This festival celebrates the fact that Peter's death confirms the queen of the Gentile world in her august prerogatives of sovereign lady, mother and bride; but the starting-point of all this greatness was the solemn moment in which the Vicar of the Man-God, shaking the dust from his feet over Jerusalem, turned his face westwards, and transferred to Rome those rights which the Synagogue had repudiated. It was on quitting Herod's prison that all this happened. "And going out of the city," says the Acts, "he went into another place." This other place, according to the testimony of history and tradition, is no other than Rome, then about to become the new Sion, where Simon Peter arrived some weeks afterwards. Thus, catching up the angel's word, the Gentile Church sings this night in one of her responsories at Matins: "Peter, arise, and put on thy garments: gird thee with strength to save the nations; for the chains have fallen from off thy hands."
For information about a special plenary indulgence that may be gained today, read here.
Saints Peter and Paul, pray for us!