Pope Francis compared the recent killing of Christians by terrorist groups such as ISIS to the persecution of the Christian church in the first century while celebrating the feast of the apostles Peter and Paul on Monday.
In his homily, Francis used a passage from the book of Acts to illustrate how the early Church was "besieged by persecution."
He said first century Christians were "harshly persecuted by Herod who 'laid violent hands upon some who belonged to the Church … proceeded to arrest Peter also … and when he had seized him he put him in prison."
Francis followed those statements by comparing what is found in Scripture to the brutalities many Christians around the world face today. He said that "these atrocious inhuman and incomprehensible persecutions," are "still present in many parts of the world today, often under the silent gaze of all."
The Pope also paid homage "to the courage of the Apostles and that of the first Christian community," and urged modern believers to follow their example.
"How many forces in the course of history have tried, and still do, to destroy the Church, from without as well as within, but they themselves are destroyed and the Church remains alive and fruitful," said Francis.
He also reminded Christians of their biblical mandate to proclaim Christ to the world while suffering through various trials or enjoying times of peace and prosperity.
"A church or a Christian who does not give witness is sterile; like a dead person who thinks they are alive; like a dried up tree that produces no fruit an empty well that offers no water," said Francis.
He also stressed prayer as the church's strongest source of strength.
"Prayer is the encounter with God, with God who never lets us down; with God who is faithful to His word; with God who does not abandon His children," continued Francis.
Pope Francis condemned terrorist groups such as ISIS and Boko Haram who are killing Christians during a mass at the Vatican in May. He said even though these groups believe they are serving God with their actions, they do not truly know him.
He referenced John 16: 2-3 where Jesus says: "The hour is coming when everyone who kills you will think he is offering worship to God. They will do this because they have not known either the Father or Me."
The Pontiff was addressing the killing of 21 Coptic Christians at the hands of ISIS militants in Libya that took place earlier this year.
"I called to mind his faithful, who were slaughtered on the beach because they are Christians. Because of the strength given them by the Holy Spirit, they were not scandalized," said Francis. "They died with the name of Jesus on their lips. This is the power of the Spirit. Witness. Martyrdom is the supreme witness."