The prayer invokes St. Peter the Apostle, recalling how he was set free from his chains by God.
Sin has a tendency to enslave us, whether we realize it or not. After committing a particular sin for the first time, temptations will only increase and without God’s grace, it will likely become a habit.
This sinful habit will soon take root in our hearts, and as time passes will become much more difficult to break. In many ways we become “slaves” to this sin, always seeking an opportunity to commit it.
The most powerful way to break free from such a habit is to first go to confession and place the sin before the mercy of God. After being made clean by this holy sacrament, another way to further break the bonds of sin is to pray to St. Peterthe Apostle, reminding God how he rescued Peter from the chains of prison (cf. Acts 12).
Below is the Collect prayer from the feast of St. Peter in Chains that is celebrated on August 1. It is a beautiful prayer, one that can lead to freedom when prayed in faith.
O God, who didst deliver thy holy Apostle Saint Peter from his bonds and allow him to depart unharmed: vouchsafe, we pray thee; to deliver us from the bonds of our sins, and of thy mercy preserve us from all evil. Through Jesus Christ thy Son our Lord, who liveth and reigneth with thee, in the unity of the Holy Spirit, one God, world without end. Amen.