Pope Francis has focused on the common baptism that all Christians share, saying the strength of this bond is stronger than existing divisions.
"We are truly the Holy People of God, even if, due to our sins, we are not yet a people fully united," the Pope said in his Jan. 20 general audience in Rome.
"All the baptized, reborn to new life in Christ, are brothers and sisters, despite our divisions," said Francis.
The Pope's had his audience in the Vatican's Paul VI Hall, during the Week of Prayer for Christian Unity, Catholic News Agency reported.
The Week of Prayer for Christian unity runs Jan. 18-25, and is organized by the Pontifical Council for the Promotion of Christian Unity and the Commission on Faith and the Order of the World Council of Churches.
This year's theme, "Called to proclaim the mighty acts of the Lord," is taken from chapter two of the First Book of Peter, and was chosen by a group from Latvia, which is home to a strong presence of Catholic, Protestant and Orthodox Christians.
Francis referred to a 12th century baptismal font in the Lutheran Cathedral of Riga in Latvia, where St. Mainardo evangelized in his address.
In Riga, the country's oldest baptismal font, dating from the time of the Latvian evangelizer, St. Reinhard, stands at the center of the Lutheran Cathedral in the country's capital.
The placement of the font so near to the cathedral's ornate pulpit speaks of the relationship between baptism and proclamation, and the calling shared by all the baptized to proclaim the mighty acts of the Lord, the World Council of Churches says on its website.
The font, said the Pope, is sign of the origin of the faith recognized by all Christians in Latvia, and he explained that this origin "is our common baptism."
SACRAMENTAL BOND OF UNITY
The Pope referred to the Second Vatican Council document "Unitatis redintegratio," and affirmed that baptism "establishes a sacramental bond of unity which links all who have been reborn by it."
Above all, this shared baptism means that all are sinners and are in need of being saved, redeemed and freed from evil, he said.
When Christians say that they share one baptism, it's an affirmation that all of them, including Catholics, Protestants and Orthodox, share the experience of being called from "unforgiving darkness and alienation from the encounter with the living God," who is full of mercy.
Francis noted that despite our common roots, all Christians unfortunately experience egoism, which plants seeds of division, closure and contempt in our minds and hearts.
By restarting from our baptism, Christians again "plunge into the source of mercy and hope, from which no one is excluded," he said.
This experience of shared grace creates "an indissoluble bond between us Christians, such that, by virtue of baptism, we can consider ourselves truly brothers," he said.
Francis said that the more we welcome this grace and mercy, the more we belong to the one, Holy People of God.
"We also become capable of announcing his marvelous works to all, beginning from a simple and fraternal witness of unity," Francis observed.
He said a good way for all Christians to work together in this announcement is by performing the corporal and spiritual works of mercy, which are "a concrete witness of unity among us Christians: Protestants, Orthodox and Catholics."
Rev. Odair Pedroso Mateus, the WCC's director of Faith and Order, said that during the week prayer, churches will have the opportunity to reflect on questions that may help them "proclaim the mighty acts of the Lord."
For example, he noted three questions that could help people focus on spiritual renewal and Christian unity:
"How do we understand our common call to be "God's people?"
Or, "In what ways do we see and respond to God's "mighty acts": in worship and song, in work for justice and peace?
"Knowing the mercy of God, how do we engage in social and charitable projects with other Christians?"
The Roman Catholic Church is not a member of the WCC, but it cooperates with the grouping of more than 550 million mainly Anglicans, Orthodox Chrsitians and Protestants in main areas and it serves on the council's Faith and Order Commission.