VATICAN CITY (AP) ― Pope Francis celebrated his first Palm Sunday Mass in St. Peter’s Square, encouraging people to be humble and young at heart and promising to go to a youth jamboree in Brazil in July, while the faithful enthusiastically waved olive branches and braided palm fronds.

The square overflowed with a crowd estimated by the Vatican at 250,000 people. Pilgrims, tourists and Romans jostled each other in an eager effort glimpse Francis as they joined the new pope at the start of solemn Holy Week ceremonies, which lead up to Easter, Christianity’s most important day.

Keeping with his spontaneous style, the first pope from Latin America broke away several times from the text of his prepared homily to encourage the faithful to lead simple lives and resist the temptation to be sad when life’s obstacles inevitably come their way. 

“Don’t let yourselves be robbed of hope! Don’t let yourselves be robbed of hope!” Francis told the crowd, in an apparent reference to the economic difficulties people are grappling with as they try to find adequate work amid a poor job market in much of the world.

At the end of the two-hour Mass, Francis took off his red vestments, and wearing his plain white cassock and skull cap, climbed into an open-topped popemobile to circle through the excited crowd. He leaned out to shake hands, kissed and patted the heads of infants passed to him by bodyguards, and often gave children the thumbs-up sign.

His security detail seemed to be reluctantly dealing with this get-close-to-the-people pontiff, scrambling around the vehicle to pick up this child or that one. At one point, the chief bodyguard, Domenico Giani, was sent back to the mother of a child he had greeted to convey a message from the pontiff, and the ever-tense Giani broke into a smile after his mission was accomplished.

Francis even climbed down from the vehicle, kissed a woman in the crowd and chatted briefly with her, and another man in the crowd leaned over a barrier to squeeze the pontiff on a shoulder _ an unheard of familiarity in the previous pontificate of the reserved Benedict XVI.

In keeping with his stress on giving examples of humility, Francis kissed the hand of an elderly woman who had outstretched an arm to him.

“There is no doubt that there will be a new spring for the church, a renewal” with this pope, said Sister Emma, an Argentine nun in the crowd.

Palm Sunday recalls Jesus’ entry into Jerusalem but its Gospel also recounts how he was betrayed by one of his apostles and ultimately sentenced to death on a cross.

Francis presided over the Mass at an altar sheltered by a white canopy on the steps of St. Peter’s Basilica.

Recalling the triumphant welcome into Jerusalem, Francis said Jesus “awakened so many hopes in the heart, above all among humble, simple, poor, forgotten people, those who don’t matter in the eyes of the world.”

Cardinals, many of them among the electors who chose him to be the Roman Catholic church’s first Latin American pope, sat on chairs during the ceremony held under hazy skies on a breezy day. He quoted from Benedict when he told the cardinals that while they are “princes” of the church, their leader is the crucified Christ, a further admonition against attachment to temporal power.

The pope ticked off a litany of evils afflicting the world, including wars, “economic conflicts that hit the weakest” as well as corruption. In the final stretch of Benedict’s papacy, the Vatican was embarrassed by a leak of documents from the papal apartment, indicating corruption, ambition and rivalries among upper ranks of the Holy See’s management.

Francis told an off-the-cuff story from his childhood in Argentina. “My grandmother used to tell us children, ‘burial shrouds don’t have’ pockets,” the pope said, in a variation of “you can’t take it with you.”

Since his election on March 13, Francis has put the downtrodden and poor at the center of his mission as pope, keeping with the priorities of his Jesuit tradition.

In his homily, Francis said Christian joy “isn’t born from possessing a lot of things but from having met” Jesus. That same joy should keep people young, he said.

“Even at 70, 80, the heart doesn’t age” if one is inspired by Christian joy, said the 76-year-old pontiff.

The pontiff said he was joyfully looking forward to welcoming young people to Rio de Janiero for the Catholic Church’s World Youth Day. So far, that is the first foreign trip on the calendar of Francis’ new papacy. “I’m coming in July,” Francis said in remarks after Mass from the esplanade of the basilica.

During Mass, at the point when the Gospel recounts the moment of Jesus’ death, many faithful knelt on hard cobblestones paving the square, and Francis knelt on a wooden kneeler.

A few young olive trees were inserted in dirt placed around the central obelisk in the square.

Holy Week will see at least one break from tradition with this new papacy. Instead of washing priests’ feet in a basilica in a symbolic gesture of humility on Holy Thursday, Francis will wash the feet of young inmates at a juvenile detention center in Rome. Other appointments in public will include the Way of the Cross procession at the Colosseum on Good Friday night. Next Sunday, Francis will celebrate Easter Mass in the square.