Sts. Marcellinus and Peter are two Roman martyrs who suffered under the Diocletian persecution, about the year 303; the first was an exorcist, the second a priest. The word martyr means witness. From the beginning, the Church has honored its martyrs. Marcellinus and Peter gave the ultimate witness to the faith, showing they were willing to die rather than lie.
After they were imprisoned they led many of their fellow prisoners to become Christian and be baptized right there in prison. They were so popular with their fellow Christians that they were secretly taken to a forest, forced to dig their own graves and there beheaded. One of the soldiers were so impressed by their courage that he became a Christian and revealed their burial place. The community came and got their bodies to give them a proper burial. Their cultus was so important that after peace was restored to the Church, Constantine built a basilica over their tomb in their honor. The names of St. Marcellinus and St. Peter are mentioned in the Canon of the Mass (Eucharistic Prayer I).
The Lives of St. Marcellinus and St. Peter
Peter, an exorcist, was cast into prison at Rome, under the emperor Diocletian, by the judge Serenus, for confessing the Christian faith. He there set free Paulina, the daughter of Artemius, the keeper of the prison, from an evil spirit which tormented her. Upon this, Artemius and his wife and all their house, with their neighbors who had run together to see the strange thing, were converted to Jesus Christ. Peter therefore brought them to Marcellinus the priest, who baptized them all. When Serenus heard of it, he called Peter and Marcellinus before him, and sharply rebuked them, adding to his bitter words threats and terrors, unless they would deny Christ. Marcellinus answered him with Christian boldness, whereupon he caused him to be buffeted, separated him from Peter, and shut him up naked, in a prison strewn with broken glass, without either food or light. Peter also he confined. But when both of them were found to increase in faith and courage in their bonds, they were beheaded, unshaken in their testimony, and confessing Jesus Christ gloriously by their blood.
Excerpted from The Liturgical Year, Abbot Gueranger O.S.B.
O God, who surround us with protection through the glorious confession of the Martyrs Saints Marcellinus and Peter, grant that we may profit by imitating them and be upheld by their prayer. Through our Lord Jesus Christ, your Son, who lives and reigns with you in the unity of the Holy Spirit, one God, for ever and ever. Amen.