Marking 1,700 years since the First Council of Nicaea, Pope Leo XIV on Friday appealed to Christians around the world to move beyond historic rifts and to recommit themselves to visible unity in Christ.

The pope delivered his message during an ecumenical prayer service at the archaeological remains of the ancient Basilica of Saint Neophytos, whose foundations lie partly submerged off the shore of Lake Iznik in northwestern Turkey. The ceremony was one of the most emblematic moments of his journey to the country, a visit centered on dialogue between Christian communities and with other religions.

“We are all called to set aside the scandal of our separations,” he said, inviting believers “to rekindle the longing for that unity for which the Lord Jesus prayed and for which he offered his life.”

Pope Leo was joined by Ecumenical Patriarch Bartholomew I, the primus inter pares among the bishops of the Eastern Orthodox Churches. Welcomed by two senior Orthodox hierarchs, the two leaders processed to a platform overlooking the ruins of the basilica, where they stood before icons of Christ and of the council and together lit candles as a sign of shared faith and hope.

Ancient Nicaea as today’s meeting place

Iznik, known in antiquity as Nicaea, lies roughly 130 kilometers southeast of Istanbul. The ruins of the early Christian basilica dedicated to Saint Neophytos—a young martyr put to death in 303 during Diocletian’s persecution—were first detected in 2014, when aerial photography revealed the outline of a church beneath the waters of the lake. The building was destroyed in an earthquake in 740, leaving its remains visible today just off the shoreline.

Standing in this historic setting, Pope Leo described the anniversary as “a precious occasion to ask anew who Jesus Christ is for the men and women of our time, and who he is for each of us personally.”

He warned against reducing Christ “to a mere moral leader, a spiritual guru, or a kind of superhero,” recalling that in the fourth century Arius had denied the full divinity of the Son. The council held here, he noted, defended both the true humanity and the true divinity of Jesus.

“If God had not truly taken on our human nature, how could we, who are mortal, share in his immortal life?” the pope asked, underlining what was at stake in the Nicene debates.

Nicene Creed as a bond of communion

Pope Leo stressed that the faith professed at Nicaea remains a cornerstone for unity among Christians across the globe. Quoting the Creed, he highlighted the confession of Christ as “consubstantial with the Father,” calling it “a deep bond that already links all who confess his name.”

Citing Saint Augustine, he added that although Christians are many, “in the one Christ, we form a single body.”

A reconciled and united Christianity, he said, would be able “to offer a persuasive witness to the Gospel” and “to become a sign of hope for all peoples.”

Beyond the Christian world: a call to fraternity

The pope extended his appeal beyond the boundaries of the Church, insisting that a genuine acknowledgment of God as Father necessarily leads to recognizing every person as a brother or sister.

He cautioned against the misuse of religion “to legitimize war, violence, or any kind of extremism or fanaticism,” urging instead a path of “fraternal encounter, patient dialogue, and concrete cooperation” among believers of all traditions.

Ecumenical and interreligious steps in Turkey

Pope Leo’s program in Turkey features a series of meetings aimed at strengthening ties between Churches. Among them is the planned signing of a joint declaration with Patriarch Bartholomew I on Nov. 29 at the Patriarchal Palace, a gesture intended to reaffirm their shared commitment to the path toward full communion.

The visit also carries an explicitly interreligious character. Earlier on Friday, the pope met with the Chief Rabbi of Turkey, presenting his pilgrimage as a sign of peace and as encouragement for all religious communities in the country.

On Saturday, Nov. 29, Pope Leo is scheduled to enter the Sultan Ahmed Mosque, further underscoring his desire to promote mutual respect and friendship among Christians, Muslims, and Jews in the land that once hosted the Council of Nicaea.