It was credited with revolutionising Catholic relations with Judaism: Wednesday marks the 50th anniversary of the Church's "Nostra Aetate" declaration which challenged religious prejudices and urged bridge building with other faiths.
A special papal audience for interfaith relations will be celebrated in Saint Peter's Square to remember the moment on October 28, 1965, when Paul VI adopted what was a ground-breaking declaration lambasting anti-Semitism in particular.
The "Nostra Aetate" -- Latin for "In Our Time" -- was drawn up at the end of the Second Vatican Council and repudiates the centuries-old charge that all Jews should be held responsible for the death of Jesus.
"The Jews should not be presented as rejected or accursed by God," the document said, insisting that Christians should decry "hatred, persecutions, displays of anti-Semitism directed against Jews at any time and by anyone".
Critics said the document did not go far enough to apologise for Christian persecution of Jews as so-called "Christ slayers" -- a label that had fuelled anti-Semitism in Europe.
But experts say it did a great deal to expunge the "blood curse", so-called because of a passage in the bible in which Jews are portrayed despairing that Jesus's "blood is on us and on our children".
Marking the anniversary, the Anti-Defamation League, which fights anti-Semitism, called it "arguably the most important moment in modern Jewish-Christian relations".
The document, adopted by cardinals and bishops around the world, also reaches out to Hindus, Buddhists and Muslims, underlining common points between the faiths and urging mutual understanding and respect.
- Church teaching 'can change' -
Interfaith expert Maureen Fiedler, writing for the National Catholic Reporter, said that the wider significance of "Nostra Aetate" was that it shows "common church teaching CAN be changed".
She said it would raise the question within the Church of "why not (change) other teachings that are harmful to groups of people", just days after the closure of a council which stumbled over issues such as divorced people and homosexuals.
Pope Francis moved quickly after his election in 2013 to make overtures to Jews and Muslims, inviting two old friends from Buenos Aires -- a rabbi and Muslim professor -- on a trip to the Middle East where he condemned religious hate.
And he was not the first pontiff to do so: John Paul II set up a series of interreligious meetings in Assisi in central Italy from 1986, which were taken up by his successor Benedict XVI, and saw atheists join the roundtable too.
John Paul II also became the first pope in the history of the Church to make an official visit to a synagogue.
All three -- John Paul II, Benedict and Francis -- have prayed with imams in mosques, the Argentine visiting Istanbul's Blue Mosque last year and planning a stop at the Koudoukou mosque in the Central African Republic (CAR) next month.
But the Catholic Church has found it harder to bridge differences with Islam than with Judaism.
Benedict XVI angered the Muslim world with a speech in 2006 in which he appeared to endorse the view that Islam is inherently violent, sparking deadly protests in several countries as well as attacks on Christians.
Since then the Vatican's pontifical council for interreligious dialogue has been working overtime to mend fences with moderate Islam -- a task made no easier by the rise of the Islamic State group in Iraq and Syria.
Francis's suggestion at the end of last year that Muslims were not doing enough to counter terrorism was feared to have increased tensions between the West and Islam, though supporters said he was right to speak out.
The 78-year-old leader has repeatedly insisted religious beliefs must not be "abused in the cause of war and violence", and makes a point of organising sessions with Buddhist, Hindu, Muslim, and Christian leaders during his travels.