What is the traditional Sunday blessing that popes deliver in St. Peter's Square?

VATICAN CITY — For thousands of Catholic pilgrims in Rome, it's the unmissable Vatican appointment: the midday Sunday blessing the pope delivers from a window overlooking St. Peter's Square.

The new pope, Leo XIV, is scheduled to deliver his first such prayer on Sunday from the loggia where he first appeared in public after being elected three days ago. His most recent predecessors delivered Sunday blessings, including their first, from a window in the Apostolic Palace overlooking the square.

Here is a look at the history, meaning and memorable moments from Sunday blessings of popes past.

The history of the pope's Sunday blessing

In 1954, which he had declared a special year of veneration to the Virgin Mary, Pope Pius XII started reciting in public a traditional Catholic midday prayer to her. He first delivered it from the pope's summer residence, just outside Rome, at Castel Gandolfo.

Back at the Vatican, he kept it up from a window facing St. Peter's Square at the Apostolic Palace, the 16th-century building where the papal apartments are. Pope Francis broke with tradition by living at a Vatican guest house instead, but still maintained the Sunday prayer tradition from the palace.

It's become a chance for ordinary faithful to see the pope relatively up close. Especially since the papacy of St. John Paul II – from 1978 to 2005 – popes have added short messages touching on different topics of the day.

When a pope misses the weekly occasion, as Francis did earlier this year during his hospitalization, it makes global news.

The Vatican announced Leo would deliver his first such prayer on Sunday, which is coincidentally Mother's Day in Italy and the United States, among other countries.

The prayer to Mary

The Angelus is the short prayer to Mary that many Catholics recite daily.

Often prayed before Mass, but traditionally accompanied by the tolling of bells at dawn, midday and early evening, it references the moment when the Gospels say the Archangel Gabriel told Mary she would become the mother of God, and she accepted.

''Angelus'' is Latin for angel, and the prayer's first verse is ''The Angel of the Lord declared unto Mary.'' The faithful then answer, ''And she conceived of the Holy Spirit,'' followed by a Hail Mary and a few more verses and prayers.

This ''annunciation'' scene is so pivotal in Christian dogma that it's been represented by some of the most celebrated painters for centuries. Some artists have also portrayed the faithful reciting the Angelus, a practice that is believed to have started in the Middle Ages.

During Eastertime – the current liturgical season, spanning 50 days from Easter Sunday to Pentecost – the prayer is substituted with another devotion to Mary, the Regina Coeli (also spelled Caeli, Latin for ''Queen of Heaven'') that encourages rejoicing in Christ's resurrection.

Memorable Sunday prayer moments

Looking frail, St. John Paul II appeared at his hospital window for his last Angelus prayer less than three weeks before he died in 2005. He didn't speak, only blessing the crowd with an olive branch. An archbishop delivered his message, with the trademark exhortation to young people not to be afraid to follow Jesus.

Tens of thousands of people packed St. Peter's Square when Pope Benedict XVI gave his final Sunday prayer in 2013 before becoming the first pope in 600 years to resign. They cheered him on as he reassured the faithful he wasn't abandoning the church, but rather turning to prayer because of his advancing age.

At his first Angelus in 2013, Francis introduced a key motif of his papacy: mercy. ''A bit of mercy makes the world less cold and more just,'' he told the crowd.

More recently, Francis used the Sunday blessings to call for peace, especially in Ukraine and Gaza. But he also would close his blessings with the down-to-earth phrase: ''Have a good lunch."

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