Pope Francis captivated a giant audience during his tour of the United States on Saturday by extolling the virtue of compassion for immigrants and praising the ideals of religious freedom. Speaking to a crowd of more than 40,000 gathered outside of the famed Independence Hall in Philadelphia, he received an excited response to his urging that the United States live up to its historical call to welcome the world's tired, poor and huddled masses yearning to breathe free.

"I ask you not to forget that like those who came before you, you bring many gifts to this great nation," Pope Francis said in his native Spanish. He urged recent immigrants to the U.S. not to be discouraged in spite of the difficult challenges they face after the journey and decision to move to the country. "Society is weakened wherever and whenever injustice prevails," the pope said.

The pontiff has stressed the message of acceptance of immigrants numerous times during his first-ever visit to the United States. He spoke about it while addressing the U.S. Congress during his visit to Washington and while celebrating mass in New York's celebrated Madison Square Garden arena, drawing a crowd of more than 20,000 to a venue best known for sports events and celebrity concerts.

RTX1SNAV Pope Francis arrives at Independence Mall in Philadelphia, Sept. 26, 2015. Photo: Reuters

Before leaving New York on his way to Philadelphia, the pope asked his helicopter crew to circle around one of the most renowned symbols of immigration and the bright future for immigrants that the United States touts as a legacy. 

"As we circled Ellis Island, as we circled the Statue of Liberty, I could see he was very 'commosso,' as they say in Italian," Cardinal Timothy Dolan, who was on the flight with the holy leader, said. "Commosso" means "moved" in Italian.

Pope Francis arrived in the United States Sept. 22 fresh off of a trip to Cuba. He has brokered diplomatic relations between that country and the U.S., and played an important part in the thawing relationship between the countries announced last year.

Before returning home, Pope Francis was scheduled to meet with inmates in a Pennsylvania prison. The pope has made a point of visiting prisons while on trips abroad. As with immigrants, it's an area he upholds in his commitment to society's outcasts. Inmates at the Curran-Fromhold Correctional Facility have spent a month constructing a chair they plan to present to the pontiff during his visit.

Pope Francis' message of acceptance comes at a particularly salient time. Immigration reform has become a central issue in the 2016 presidential nomination race. Some Republicans have advocated deporting all of the estimated 11 million undocumented immigrants in the U.S., and the conversation seems unlikely to conclude soon.