The Holy Spirit seems to be a "luxury prisoner" in many Christians' hearts: someone who is welcomed to stay, but not allowed to act or move us forward, the Pope said during his homily at Mass on Monday.

"We keep the Holy Spirit as a 'luxury prisoner' in our hearts: we do not allow the Spirit to push us forward, to move us. The Spirit does everything, knows everything, reminds us what Jesus said, can explain all about Jesus," the Holy Father said May 9 during his Mass at the chapel of Casa Santa Marta  in the Vatican.

In the day's reading, when St. Paul speaks with the disciples in Ephesus (Acts 19: 1-8), Pope Francis pointed out that they had "not even heard that there is a Holy Spirit."

Likewise, while Christians today have a knowledge of the Holy Spirit as part of the Holy Trinity, they do not know what the Spirit's role is in the Church.

"The Holy Spirit is the one who moves the Church, the one who works in the Church and in our hearts," the Roman Pontiff said.

The Third Person of the Trinity is "the protagonist of the Living Church," he said, while cautioning against simply reducing the Christian life to a code of "morals and ethics."

The faith, the Pope said, is something more. It "is not just an ethical life: it is an encounter with Jesus Christ."

The Holy Spirit "frees us from the 'orphan-like' condition which the spirit of the world wants to put us in."

"The Holy Spirit is the one who "moves us to praise God, to pray to the Lord" and who "teaches us to see the Father and call him 'Father.'"

There is one thing the Holy Spirit "can't do" the Pope said: "The Holy Spirit cannot make us 'virtual' Christians who are not virtuous." Instead, "The Holy Spirit makes real Christians. The Spirit takes life and prophetically reads the signs of the times pushing us forward."

Ahead of Pentecost Sunday the Holy Father invited Christians to prepare by opening up our hearts to the Holy Spirit.

"This is what we must do this week: think of the Spirit and talk to him."

Pope Francis also greeted the Vincentian Sisters of Charity who work in Casa Santa Marta. Today they are celebrating the feast of St. Louise de Marillac who, along with St. Vincent de Paul, founded their order.