PHILADELPHIA—Pope Francis on Sunday addressed the scourge of clergy sex abuse, vowing that the Catholic Church would provide “careful oversight” to protect young believers.

In unscripted remarks at the beginning of his address to bishops, Francis said “great harm” was caused by the clergy sex abuse scandal that has marred the church over the last decade. Francis said he met with survivors of clerical sex abuse on Sunday and promised to hold clergy responsible for abuse accountable.

“Those who have survived have become true heralds of mercy,” Francis said.  “Humbly we owe each of them our gratitude for their courage.”

“God weeps,” he added.

The comments on clergy sex abuse from Francis comes as he prepares to wrap up his U.S. tour, a historic visit which will culminate with an outdoor Mass in the City of Brotherly Love that organizers say will draw hundreds of thousands of participants.

The Vatican said Francis met with five adult survivors–three women and two men–who had suffered abuse by clergy, family members or teacher when they were minors. Each survivor was accompanied by family member or another supporter.

The meeting was also attended by Cardinal Sean Patrick O’Malley, the archbishop of Boston who is overseeing a church commission focused on the protection of minors; Philadelphia Archbishop Charles Chaput, and Bishop Michael Fitzgerald, who heads the Philadelphia diocese office for protection of minors.

“The Pope spoke with visitors, listening to their stories and offering them a few words together as a group and later listening to each one individually,”  Vatican spokesman Federico Lomobardi said in a statement. “He then prayed with them and expressed his solidarity in sharing their suffering, as well as his own pain and shame in especially the case of injury caused them by clergy or church workers.”

Allegations of sexual abuse by priests date back decades, but exploded into a crisis for the church in the U.S. more than a decade ago following news reports detailing a litany of abuses and cover-ups by American bishops.

Francis addressed the clergy abuse issue during his visit in Washington, but some survivors said that his words were not enough.

“What sacrifice?” said Barbara Blaine of Chicago, the president of Survivor’s Network of Those Abused by Priests. “What bishop takes fewer vacations, drives a smaller car, does his own laundry or has been passed over for promotion because he’s shielding predators and endangering kids? None.”

Before Francis, who made stops in Washington and New York before arriving in Philadelphia on Saturday, celebrates Mass on the Benjamin Franklin Parkway, he met with bishops and will later meet with prison inmates.

In his address to the bishops, Francis focused on the difficulties of supporting the family structure in a rapidly changing world.

“Needless to say, our understanding, shaped by the interplay of ecclesial faith and the conjugal experience of sacramental grace, must not lead us to disregard the unprecedented changes taking place in contemporary society, with their social, cultural – and now juridical – effects on family bonds,” Francis said. “These changes affect all of us, believers and non-believers alike. Christians are not “immune” to the changes of their times.

After meeting with the bishops, Francis is scheduled to visit the Currran-Fromhold Correctional Facility, where he’s expected to meet with dozens of inmates. Francis is expected to offer the prisoners—which included suspected murders, rapists and mobsters—words of hope and speak to them about forgiveness and redemption.

On Saturday, Francis delivered an impassioned address before a crowd of 40,000 in which he focused on his concerns about religious freedom and immigration.

Speaking to a jubilant audience from outsideIndependence Hall, Francis called it an honor to stand at the doorstep of where the Declaration of Independence was drafted. But he also underscored that the principles set out in the country’s founding document need to be “constantly reaffirmed.”

“The history of this nation is also the tale of a constant effort, lasting to our own day, to embody those lofty principles in social and political life,” said Francis, who spoke from the same lectern used by Abraham Lincoln to deliver the Gettysburg Address, the Civil War speech that not only delved into the importance of keeping the Union intact but also focused on human dignity. “This shows that, when a country is determined to remain true to its founding principles, based on respect for human dignity, it is strengthened and renewed.”

The speech, at such a potent symbol of American history, offered grist for Americans on the political right and left.

He expressed concerns about “various forms of modern tyranny” leading to religious freedom being reduced to “a subculture.”

We live in a world subject to the ‘globalization of the technocratic paradigm’ which constantly aims at a one-dimensional uniformity and seeks to eliminate all differences and traditions in a superficial quest for unity,” he said.

The remarks on religious freedom come after Francis made a surprise visit while in Washington to the Little Sisters of the Poor, the nuns who are suing the Obama administration over the requirement that employers cover the cost of birth control. The Vatican said that the visit was meant to show a sign of support for the nuns in their battle over the reform that came with President Obama’s signature health care law. The Little Sisters maintain that their religious freedoms are violated by the birth control requirement.

Francis also weighed in on immigration, at a moment when the issue has come into focus in the 2016 presidential campaign. Donald Trump, the current front-runner for the GOP nomination, has spoken perhaps most provocatively about immigration — calling for building a wall on the U.S.-Mexico border to keep out people he has labeled as “rapists” and “criminals.”

Francis, the Argentinean son of immigrants, struck on the issue of migrants fleeing conflict in Syria in his speech before Congress earlier this week. He called on U.S. lawmakers to not be “taken aback” by their numbers, but to be mindful of their personal stories and often tragic circumstances.

But the issue was put in greater focus in his address at Independence Hall, where he was greeted by a crowd that waved flags from Argentina, Brazil, Ecuador and Mexico.

Francis noted that among the crowd were members of “America’s large Hispanic population,” who he said had come to the U.S. at great personal cost. He told them they should not be “discouraged by whatever challenges and hardships you face.”

“I ask you not to forget that, like those who came before you, you bring many gifts to your new nation,” Francis said. “You should never be ashamed of your traditions.”

Francis wrapped up his Saturday night in Philadelphia at an event, emceed by actor Mark Wahlberg, where he heard from Catholic families. The pope called families “a factory of hope”

“Father, you speak like that because you’re not married,” Francis said. “Families have difficulties. In families we quarrel. Sometimes, plates can fly. Children cause headaches. I won’t speak of mother-in-laws.

“But in families, there is always light,” he said.