Vatican City, Jan 15, 2016 / 04:07 pm (CNA/EWTN News).- On Sunday Pope Francis will become the third pontiff to cross the threshold of the Major Temple in Rome, the most important and significant synagogue in the city.

Thirty years have passed since the historic visit of John Paul II in 1986, and in these decades the relationship between Jews and Catholics has become closer, more intense, and, because of this, not absent of difficulty.

St. John Paul II brought the spirit of Nostra Aetate into the synagogue, making the historic document that reshaped Catholicism’s relationship with Judaism concrete when in 1986 he became the first Pope since the first century to ever set foot in a synagogue.

But the story as to how John Paul II’s decision to visit Rome’s Major Synagogue came about has a little-known twist, beginning with the planning of an international papal trip.

In an interview with CNA, Gianfranco Svidercoschi, a longtime Vatican correspondent, the former vice-director of the Vatican newspaper L'Osservatore Romano and a biographer of St. John Paul II, recounted the story.

He said that Fr. Roberto Tucci, former president of Vatican Radio and the previous organizer of papal trips, had been sitting with John Paul II discussing his upcoming 1987 visit to the United States.

“Among the various invitations, one was from an American rabbi who asked the Pope to visit his synagogue,” Svidercoschi said, adding that John Paul II was “very much in favor of it, of course, seeing as how in 1985 he wasn't afraid, at the White House, to meet with young Muslims.”

But it was at this point that Fr. Tucci “had an intuition: 'if a Pope is going to a synagogue, the first needs to be the Synagogue of Rome.'”

So, it was following this train of thought that St. John Paul II decided to visit the Synagogue of Rome, becoming the first Pope in modern history to do so. From that historic gesture in 1986, it has almost become a habit.

Rabbi Elio Toaff, Chief Rabbi of Rome at the time, was the first to go and meet John Paul II in a visit to the parish of San Carlo ai Catinari in 1981. But then the next year, on April 13, 1986, the story took a great leap forward.

After John Paul II’s revolutionary embrace with Toaff, a great promoter of dialogue, the speech of the Polish Pope who had grown up with Jewish friends in Krakow was a lesson on the Second Vatican Council.

The Pope gave his thanks and recalled the many efforts of Pope St. John XXIII, who laid the groundwork for Nostra Aetate, and expressed his “abhorrence” for the Nazi genocide.

He also remembered how the Church came to the aid of Jews during the dark years of persecution in the Second World War by opening the doors of their convents and seminaries to those who went into hiding.

The Pope noted that the relationship Christians have with the Jews is one that they don’t have with any other religion, and pointed to common areas of collaboration in a society that has forgotten the sacred. He then asked for help from the Jewish community, the oldest in Rome, in making Rome a better city.

Many years then passed before another, historic visit took place. The German Pope Benedict XVI arrived to the Seat of Peter, and first wanted to visit the synagogue in Cologne, a tragic reminder of the “Kristallnackt,” or “the Night of Broken Glass.”

The Kristallnackt refers to a massive, coordinated attack against the Jews that took place throughout the German Reich the night of Nov. 9, 1938.

While in Cologne for World Youth Day in 2005, Benedict XVI visited the city’s synagogue, and recalled the 60 years since the liberation from the Nazis.

In his speech, Benedict resumed the path of John Paul II, and took another step forward, condemning the antisemitism which in Europe raises its head like a dragon all too often. He also drew attention to the commitment of the German bishops, and said that we must love one another and put the Ten Commandments again at the center of Jewish-Christian dialogue.

From there, Benedict XVI’s reflections began again when on Jan. 17, 2010, just six years ago, he crossed the threshold of Rome’s Major Temple as a symbol of the “emancipation” of the Jews in Rome.

Rabbi Toaff had by then aged and become ill, but still wanted to greet the Pope. So Benedict went to his house and this time, the first embrace took place in his doorway.

In the synagogue to welcome Pope Benedict after was Rabbi Riccardo Di Segni. It will also be he who receives Pope Francis this Sunday, Jan. 17.

“How good it is for brothers to be together,” the German Pope had said. And in one act the misunderstandings that often punctuate dialogue between Catholics and Jews seemed to dissolve.

Then he gave his reflection, almost in a rabbinic style, on the commandments and on mercy.

One mustn’t forget the destruction of the extermination, he said; a German, who had visited Auschwitz asking for forgiveness. “How is it possible,” he said in the synagogue, “to forget their faces, their names, their tears – the desperation of men, women and children?”

Benedict retraced the common values of the two religions, from safeguarding life to caring for creation.

Then, on the Ten Commandments, he said that “all of the commandments are summed up in the love of God and in mercy toward others.”

The key to everything, the point of union, is the mercy which “urges Jews and Christians to exercise, in our time, a special generosity towards the poor, towards women and children, strangers, the sick, the weak and the needy,” he said.

“In the Jewish tradition there is a wonderful saying of the Fathers of Israel: ‘Simon the Just often said: The world is founded on three things: the Torah, worship, and acts of mercy,’ he said.

In exercising justice and mercy, “Jews and Christians are called to announce and to bear witness to the coming Kingdom of the Most High, for which we pray and work in hope each day,” Benedict XVI continued.

Pope Francis, for whom mercy has been the center of his pontificate, will arrive to the synagogue in the Holy Year of Mercy with a personal history of relationships with Jewish friends from Buenos Aires.

Perhaps his reflection will also be on that very subject of mercy, from the faith of brothers.