Pope Francis celebrated evening prayer at the end of the Week of Prayer for Christian Unity tonight, stressing the nature of ecumenism as a journey that requires perseverance.

"Christ, dear friends, cannot be divided! This conviction must sustain and encourage us to persevere with humility and trust on the way to the restoration of full visible unity among all believers in Christ," said the Pope in his homily at Vespers on Jan. 25.

"As we look with gratitude to the progress which the Lord has enabled us to make, and without ignoring the difficulties which ecumenical dialogue is presently experiencing, let us all pray that we may put on the mind of Christ and thus progress towards the unity which he wills," he urged.

Christian leaders, including representatives from the Orthodox Church and Anglican communion, as well as faithful from around the world, gathered in prayer at the Basilica of St. Paul Outside the Walls in Rome on Saturday evening as the Bishop of Rome reflected on the journey of ecumenism traveled by his predecessors.

"Tonight I think of the work of two great Popes: Blessed John XXIII and Blessed John Paul II. In the course of their own lives, both came to realize the urgency of the cause of unity and, once elected to the See of Peter, they guided the entire Catholic flock decisively on the paths of ecumenism," noted Pope Francis.

"With them, I think too of Pope Paul VI, another great promoter of dialogue; in these very days we are commemorating the fiftieth anniversary of his historic embrace with the Patriarch Athenagoras of Constantinople," recalled the Pontiff, referring to the 1964 meeting between the leaders of the Catholic and Orthodox Churches which the lifted the centuries-long excommunications issued against one another.

Such efforts "enabled ecumenical dialogue to become an essential dimension of the ministry of the Bishop of Rome, so that today the Petrine ministry cannot be fully understood without this openness to dialogue with all believers in Christ."

It is "Christ alone" who is "the principle, the cause and the driving force behind our unity," stressed Pope Francis.

"This evening, as we gather here in prayer, may we realize that Christ, who cannot be divided, wants to draw us to himself, to the sentiments of his heart, to his complete and confident surrender into the hands of the Father, to his radical self-emptying for love of humanity."

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Christ's total love allows his followers to "realize all the more that we may not regard divisions in the Church as something natural, inevitable in any form of human association."

Rather, the Pope emphasized, "our divisions wound Christ's body, they impair the witness which we are called to give to him before the world."

Closing with a prayer, Pope Francis requested, "Dear brothers and sisters, let us ask the Lord Jesus, who has made us living members of his body, to keep us deeply united to him, to help us overcome our conflicts, our divisions and our self-seeking, and to be united to one another by one force, by the power of love which the Holy Spirit pours into our hearts. Amen."