A day after becoming the first North American head of the world’s Catholics, Pope Leo XIV celebrated his first Mass in the Sistine Chapel Friday where he said he hoped to bring light to “the dark nights of the world” and deplored a “lack of faith” and the pursuit of “power” and “pleasure”.

Pope Leo XIV implored clergy in church authority to “make oneself small” in order to glorify Christ, echoing a theme of his predecessor Pope Francis in his first public Mass on May 9.

“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,” Leo said a day after his election as the 267th pontiff of the Catholic Church

The first pope elected from the United States — a global superpower that many thought would disqualify any American from leading the papacy — acknowledged that he must lead by example.

Pope Leo XIV will be formally installed as pope at a Mass on May 18 and will preside over his first general audience May 21, the Vatican announced in a statement.

The Mass of Thanksgiving was celebrated in the Sistine Chapel with the College of Cardinals, notably alongside the same 133 cardinals who yesterday (May 8) cast ballots in the world’s most secretive election process in that same sacred space and stunned many around the world with their choice.

Also at the Mass were the more than 80 retired cardinals that could not participate in the papal conclave.

In a 10-minute homily that began in English before switching to Italian, Pope Leo said that he was counting on all his brother cardinals who elected him to walk with him on this journey.

In the less than 24 hours since the shock election, Leo has catapulted from a relatively unknown Chicago-born cardinal who has spent most of his life outside the United States to become the successor of Pope Francis.

During his homily, Leo paid tribute to his predecessor, saying that Pope Francis “taught us so many times, we are called to bear witness to our joyful faith in Jesus the Saviour.”

This can be difficult in today’s world, he said, where Christianity is often “considered absurd, meant for the weak and unintelligent” and “other securities are preferred, like technology, money, success, power or pleasure.”

Preaching the Gospel and bearing witness to its truth is not easy, Leo said.

“Believers are mocked, opposed, despised or at best tolerated and pitied,” Leo said. “Yet, precisely for this reason, they are the places where our missionary outreach is desperately needed.”

Leo said that a lack of faith has often resulted in a “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.”

The task of all Christians — beginning with the leader of the Catholic Church, he said — is to commit to a “daily journey of conversion” of “fidelity to the Lord and bringing the Good News to all.”

During the Mass, Scripture was read in both English and Spanish — a nod to the new pope’s missionary work in both the United States and Peru.

On Thursday evening (May 8), following his election, he returned to the Vatican residence inside the palazzo that also houses the Vatican’s doctrinal office where he lived, greeting many neighbours and building personnel. In photos that have appeared on social media, he posed for selfies with Vatican officials and even gave an autograph to a young girl.

The new pope will deliver his first Regina Coeli address at noon Sunday (May 11) from the balcony of the Vatican’s Apostolic Palace.