Pope Leo XIV celebrated his first Mass as pontiff in the Sistine Chapel on Friday, delivering a passionate speech that stressed the importance of spreading God’s word in a world that sometimes “mocks” faith.

Wearing a white robe and holding a gold crucifix, the first American pontiff addressed the cardinals who elected him in a historic vote the day before, calling his new role an honor and a heavy responsibility.

“You have called me to carry that cross and to be blessed with that mission, and I know I can rely on each and every one of you to walk with me as we continue as a church, as a community, as friends of Jesus, as believers, to announce the good news, to announce the Gospel,” former Cardinal Robert Francis Prevost, 69, of Chicago said in English.

The new pope stood at an altar next to the Michelangelo painting “The Last Judgment” and warned against “practical atheism” among Christians who believe Jesus is a “charismatic leader” instead of a savior.

“Even today, there are many settings in which the Christian faith is considered absurd, meant for the weak and unintelligent. Settings where other securities are preferred, like technology, money, success, power, or pleasure,” Pope Leo said in Italian in his homily.

“These are contexts where it is not easy to preach the Gospel and bear witness to its truth, where believers are mocked, opposed, despised, or at best tolerated and pitied.” 

But Pope Leo — known for his devoted missionary work in impoverished parts of Peru — said places where faith is rejected are often the areas that need it most.

“A lack of faith is often tragically accompanied by the loss of meaning in life, the neglect of mercy, appalling violations of human dignity, the crisis of the family and so many other wounds that afflict our society,” he stressed.

In his first appearance to the world as pope Thursday evening, Leo wore the papacy’s traditional red cape— which Pope Francis rejected on his election in 2013 — hinting at a return to rule-following after his predecessor’s relatively unorthodox leadership.

But in naming himself Leo XIV— after the 19th century social-justice reformer pope and referring to some of Francis’ priorities — the new pontiff signaled he also may want to continue to take the Church in the same direction.

During his homily Friday, the pontiff referenced a bible passage in which St. Ignatius declared, “I will truly be a disciple of Jesus Christ, when the world no longer sees my body” — championing it as an example of letting go of ego to connect with God.

“Ignatius was speaking about being devoured by wild beasts in the arena — and so it happened — but his words apply more generally to an indispensable commitment for all those in the Church who exercise a ministry of authority,” he said.

“It is to move aside so that Christ may remain, to make oneself small so that he may be known and glorified, to spend oneself to the utmost so that all may have the opportunity to know and love him.”

Francis, the first Latin American pope, appeared to have his eye on Prevost and saw him as his heir apparent, sending him to take over a complicated diocese in Peru in 2014.

Francis then brought Prevost to the Vatican in 2023 to head its powerful Dicastery for Bishops, which vets bishop nominations around the world and is one of the most vital jobs in church governance.

Earlier this year, Francis promoted Prevost into the senior ranks of cardinals, giving him prominence going into the conclave that few other cardinals had.

He also presided over one of the most revolutionary reforms Francis made — adding three women to the voting group that decides which bishop nominations to forward to the pope.

There had long been a taboo on a US pope, given America’s superpower status in the secular world. But Prevost prevailed possibly because he’s also a Peruvian citizen who had lived in the country for two decades, first as a missionary and then as bishop.

Since arriving in Rome for his work with Francis, Prevost had kept a low public profile but was well-known to church power players and respected by those who worked with him.

On Thursday, the crowd in St. Peter’s Square erupted in cheers when white smoke poured out of the Sistine Chapel shortly after 6 p.m. on the second day of the conclave, signaling a new pontiff had been chosen.

Waving flags from around the world, tens of thousands of people were surprised an hour later when the senior cardinal deacon announced the selection was Prevost.

“Together, we must try to find out how to be a missionary church, a church that builds bridges, establishes dialogue, that’s always open to receive — like on this piazza with open arms — to be able to receive everybody that needs our charity, our presence, dialogue and love,” Pope Leo said in his first comments to the world as pope Thursday evening.

President Trump said it was “such an honor for our country” for the new pope to be American.

The president added that “we’re a little bit surprised, and we’re happy.”

Prevost has been critical of the Trump administration’s immigration policies. In past social media posts, Prevost shared articles bashing Vice President JD Vance’s justification of the administration’s mass deportation plans.

Vatican watchers said Prevost’s decision to name himself Leo was particularly significant given the previous Pope Leo’s legacy of social justice and reform, suggesting continuity with some of Francis’ chief concerns.

Specifically, Leo cited one of Francis’ key priorities of making the Catholic Church more attentive to lay people and inclusivity, a process known as synodality.

“He is continuing a lot of Francis’ ministry,’’ said Natalia Imperatori-Lee, the chair of religious studies at Manhattan University in The Bronx.

She also said his election could send a message to the US church, which has been badly divided between conservatives and progressives, with much of the right-wing opposition to Francis coming from there.

“I think it is going to be exciting to see a different kind of American Catholicism in Rome,’’ Imperatori-Lee said.

Prevost said in a 2023 interview with Vatican News that the polarization in the church was a wound that needed to be healed.

“Divisions and polemics in the church do not help anything. We bishops especially must accelerate this movement towards unity, towards communion in the church,” he said.

Archbishop Bernard Hebda of the Archdiocese of St. Paul and Minneapolis told reporters he never thought he would see an American pope, given the questions of how one would navigate dealing with a US president, especially someone like Trump.

“And so I just never imagined that we would have an American pope, and I have great confidence that Pope Leo will do a wonderful job of navigating that,” he said.

Leo’s brother, John Prevost, was so shocked that his brother had been elected pope that he missed several phone calls from Leo during an interview Thursday with The Associated Press.

He called the pope back and said Leo told him he wasn’t interested in being part of the interview.

John Prevost described his brother as being very concerned for the poor and those who don’t have a voice. He said he expects him to be a “second Pope Francis.

“He’s not going to be real far left and he’s not going to be real far right,” he added. “Kind of right down the middle.”

In his first hours as pope, Leo went back to his old apartment in the Sant’Uffizio Palace to see colleagues, according to selfies posted to social media. Vatican Media also showed him in the moments after his election praying at a kneeler in the Pauline Chapel before emerging on the loggia.

On Sunday, he is scheduled to deliver his first noon blessing from the loggia of St. Peter’s and attend an audience with the media Monday in the Vatican auditorium, Vatican spokesman Matteo Bruni said.

He also has possible foreign-trip plans at the end of May. Francis had been invited to travel to Turkey to commemorate the 1,700th anniversary of the First Council of Nicaea, a landmark event in Christian history and an important moment in Catholic-Orthodox relations.

The new pope was formerly the prior general, or leader, of the Order of St. Augustine, which was formed in the 13th century as a community of “mendicant” friars — dedicated to poverty, service and evangelization. Vatican News said Leo is the first Augustinian pope.

In Peru, he is known as the saintly missionary who waded through mud after torrential rains flooded the region, bringing help to needy people, and as the bishop who spearheaded the lifesaving purchase of oxygen production plants during the COVID-19 pandemic.

“He has no problem fixing a broken-down truck until it runs,” said Janinna Sesa, who met Prevost while she worked for the church’s Caritas charity.

-With Post Wires