Vatican City, Sep 13, 2019 / 05:11 am (CNA).- In a letter to Bartholomew I of Constantinople, Pope Francis has explained the unexpected gifting of a relic of St. Peter to the leader of the Eastern Orthodox Church in June, a gesture which generated controversy among some Catholics.

The pope wrote to the ecumenical patriarch Aug. 30, saying the decision to give the relic was born out of prayer and intended as a sign of the ongoing work and prayer toward visible communion between the Orthodox and Catholic Churches.

Pope Francis gave the relic to a member of a delegation from the Ecumenical Patriarchate of Constantinople, which attended a Mass in St. Peter’s Basilica for the feast of Saints Peter and Paul June 29.

After the Mass, Pope Francis brought Eastern Orthodox Archbishop Job to a chapel in the papal apartments and offered the chapel’s reliquary as a gift. The bronze box contains nine fragments from what are believed to be the bones of St. Peter in the necropolis beneath St. Peter’s Basilica.

The box bears the inscription, “From the bones found in the hypogeum of the Vatican Basilica, which are believed to be of Blessed Peter the Apostle.”

When Pope St. Paul VI discovered St. Peter’s relics during excavations in 1939, he had the fragments removed to keep in the private chapel of the papal apartments.

“This gesture is intended to be a confirmation of the journey that our Churches have made in drawing closer to one another: a journey at times demanding and difficult, yet one accompanied by evident signs of God’s grace,” Francis wrote to Bartholomew Aug. 30.

“I sensed that this thought came to me from the Holy Spirit, who in so many ways prompts Christians to regain that full communion for which our Lord Jesus Christ prayed on the eve of his glorious Passion.”

Pope Francis said he was reflecting on the “mutual determination to advance together towards full communion,” and thought of a gift Patriarch Athenagoras gave to St. Paul VI of an icon of Saints Peter and Andrew embracing.

This icon, he said, “has become for us a prophetic sign of the restoration of that visible communion between our Churches to which we aspire and for which we fervently pray and work.”

“Hence, in the peace born of prayer, I sensed that it would be highly significant were some fragments of the relics of the Apostle Peter to be placed beside the relics of the Apostle Andrew, who is venerated as the heavenly patron of the Church of Constantinople.”

The Orthodox delegation brought the reliquary to Istanbul, where Monsignor Andrea Palmieri, undersecretary of the Pontifical Council for Promoting Christian Unity, personally gave it to Bartholomew.

Bartholomew, as patriarch of Constantinople, is regarded as “first among equals” within the Orthodox communion and is seen by many as the worldwide leader of Orthodoxy.

Orthodox Archbishop Job called the gesture “another gigantic step towards concrete unity.”

Pope Francis wrote that the joining of the relics of Andrew and Peter can serve “as a constant reminder and encouragement that, on this continuing journey, our divergences will no longer stand in the way of our common witness and our evangelizing mission in the service of a human family that today is tempted to build a purely secular future, a future without God.”