Two popes sat side by side before a crowd of rain-soaked pilgrims in St. Peter's Square May 10.

Coptic Orthodox Pope Tawadros II, patriarch of Alexandria, Egypt, was at the Vatican to mark the 50th anniversary of a joint declaration signed by St. Paul VI and Pope Shenouda III in 1973 outlining the beliefs shared by their churches.

Before his general audience, Pope Francis embraced Pope Tawadros and kissed his encolpion, an icon Orthodox and Byzantine Catholic bishops wear instead of a pectoral cross.

During the audience, the two publicly exchanged greetings and took turns addressing the crowd.

"Despite the differences in our roots and affiliations, we are united by the love of Christ who dwells within us and the host of our apostle fathers and saints who guide us," Pope Tawadros said, speaking in Arabic. "Let us walk together in life bearing in mind the promise (God) has made to us -- eternal life -- accompanying and supporting each other with prayers according to this promise."

Calling for Catholics and Copts to love one another, Pope Tawadros said that "even though we go against the tide of the greedy and selfish world, we have accepted the challenge of love that Christ asks of us, and we will be true Christians, and the world will be more human, because it will know that God is love and that this is his highest name."

After congratulating Pope Francis on the 10th anniversary of his pontificate, celebrated in March, Pope Tawadros recalled his trip to Rome and meeting with Pope Francis in 2013, which, he said, was "filled with brotherly love."

Now each year on May 10, the anniversary of the 1973 meeting between their predecessors, the two popes speak over the phone and exchange greetings. That tradition, said Pope Tawadros, "embodies the Christian spirit and love that unites us in serving God and serving our brothers and sisters in humanity."

Pope Tawadros also thanked Pope Francis for his visit to Egypt in April 2017, which he called a "great blessing for all of Egypt," and recalling Pope Francis' messages for their church communities to together become "a living image of the heavenly Jerusalem."

Putting aside his typical weekly catechesis, Pope Francis thanked Pope Tawadros for his visit to Rome and commitment to the "growing friendship" between their churches.

He referred to the 21 Coptic Christian martyrs, who he said, "are also ours," that were killed by the Islamic State in Libya in 2015, and he asked for their intercession in fostering communion between the two churches. The two popes then jointly blessed the crowd of visitors in St. Peter's Square.

Pope Tawadros was scheduled to meet privately with Pope Francis May 11 before meeting with officials from the Dicastery for Promoting Christian Unity. He also was scheduled to meet with Rome's Coptic Christian community and celebrate Divine Liturgy May 14 in the Basilica of St. John Lateran, the cathedral of Rome.

In a jointly written preface to a book about the 1973 declaration, the two popes expressed their desire for their churches to "journey toward full communion," and gave thanks for "the steps already taken, and the distance already traveled, which are often much more important than we imagine."