That number, the pope said, is not a limit and nor does it quantify justice, but rather, it "opens up a vast horizon" and "serves as the measure of a charity capable of infinite forgiveness."
After centuries of conflict among Christian communities, this charity "now allows us to come together as brothers and sisters, at peace and full of gratitude to God our Father," he said, adding that the day's gathering is the fruit of the forgiveness and efforts toward unity of many who have come before them.
"Out of heartfelt love for Jesus, they did not allow themselves to be mired in disagreements, but instead looked courageously to the future, believing in unity and breaking down barriers of suspicion and of fear," he said.
Those working in the ecumenical field today are heirs "to the faith, charity and hope of all those who, by the nonviolent power of the Gospel, found the courage to change the course of history," Francis said.
While in the past this history "had led us to mutual distrust and estrangement, and thus contributed to the infernal spiral of continual fragmentation," the Holy Spirit has changed the route, "and a path both old and new has been irrevocably paved: the path of a reconciled communion aimed at the visible manifestation of the fraternity that even now unites believers."
Pope Francis also noted that the number 70 reflects the number of disciples Jesus sent out two-by-two in the Gospel, which implies that in order to be a true disciple, one must "become an apostle, a missionary," going beyond division to spread the Good News.
Pointing to the theme of the day's meeting, "Walking, Praying and Working Together," the pope said walking is a two-fold movement which implies both going "in and out," which means going in toward the center, which is Christ, and out toward "the existential peripheries" of the world.
Prayer is "the oxygen of ecumenism," he said. "Without prayer, communion becomes stifling and makes no progress, because we prevent the wind of the Spirit from driving us forward." The pope then urged attendes to ask themselves how often they pray for one another, and for unity.
On the point of walking together, Francis pointed to several ongoing initiatives in which the Holy See already collaborates with ecumenical leaders, including the Commission on World Mission and Evangelism, collaboration with the Office for Interreligious Dialogue and Cooperation, and the joint preparation of texts for the Week of Prayer for Christian Unity, among others.
He also praised the WCC's Bossey Ecumenical Institute for their work in training both pastoral and academic leaders for different Christian churches throughout the world.
"The work of our Christian communities is rightly defined by the word 'diakonia,'" a Greek term meaning service to others, he said, adding that credibility of the Gospel "is put to the test by the way Christians respond to the cry of all those, in every part of the world, who suffer unjustly from the baleful spread of an exclusion that, by generating poverty, foments conflicts."
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With vulnerable populations becoming increasingly marginalized and the rich becoming more wealthy, and with Christian persecution increasing throughout the world, Christians themselves are called to draw near to those who suffer, remembering that unity is already established in the "ecumenism of blood," he said.
Pope Francis closed his address urging attendees to encourage one another while avoiding the temptation "to absolutize certain cultural paradigms and get caught up in partisan interests."
"Let us help men and women of good will to grow in concern for events and situations that affect a great part of humanity but seldom make it to the front page. We cannot look the other way," he said, adding that "it is problematic when Christians appear indifferent towards those in need."
More troubling still, he said, is the certainty shown by some, "who consider their own blessings clear signs of God's predilection rather than a summons to responsible service of the human family and the protection of creation."
Asking what each community can concretely do together, the pope urged participants not to hesitate in putting a plan together when ideas arise, so as to "experience a more intense fraternity in the exercise of concrete charity."
Elise Harris was senior Rome correspondent for CNA from 2012 to 2018.