Pope Francis left Philadelphia late on Sunday (Sept 27), wrapping up a historic tour of the United States. The six-day trip saw him meeting President Barack Obama, becoming the first pope to address the US Congress, leading a multi-faith prayer for world peace at Ground Zero in New York and holding a huge open-air mass in Philadelphia for hundreds of thousands of people.

Here is a look at some of the memorable quotes made by the Pope during his tour.

1. On politics and poverty

Pope Francis made history on his US trip, when he addressed a joint meeting of the US Senate and the House of Representatives on Thursday (Sept 24), becoming the first pope to do so. Pope Francis, who was greeted by applause and a standing ovation, focused his speech on persuading American lawmakers that the country's power and wealth should be used to serve humanity:

"Politics is... an expression of our compelling need to live as one, in order to build as one, the greatest common good," he said, as he urged American lawmakers to take responsibility for crafting a fairer economic system.

2. On immigration and the world's refugee crisis

Pope Francis' speech to Congress was wide-ranging as he pushed politicians to tackle global warming, restrict the arms trade and abolish the death penalty.

He also dedicated much of his speech to appealing to American lawmakers to do more to welcome immigrants. He called attention to the wave of refugees arriving in Europe from Syria, Iraq and Afghanistan, while reminding Americans of their immigrant roots and the values of the nation's founding fathers:

"Our world is facing a refugee crisis of a magnitude not seen since the Second World War. On this continent, too, thousands of persons are led to travel north in search of a better life for themselves and for their loved ones, in search of greater opportunities," he said, referring to immigrants heading to the US from Mexico and Central America.

"Is this not what we want for our own children? We must not be taken aback by their numbers, but rather view them as persons, seeing their faces and listening to their stories, trying to respond as best we can to their situation."

3. On climate change

At his appearance at the United Nations on Friday (Sept 25), Pope Francis put the spotlight on climate change as he warned that greed is destroying the Earth's resources and aggravating poverty:

"Our world demands of all government leaders a will which is effective, practical, constant, with concrete steps and immediate measures for preserving and improving the natural environment and thus putting an end as quickly as possible to the phenomenon of social and economic exclusion, with its baneful consequences."

Pope Francis earlier this year published the first papal encyclical, a letter to the church, dedicated to the environment.

4. On the plurality of faith

Leading a multi-faith prayer for world peace at Ground Zero - the site of the Sept 11, 2001 attacks that killed nearly 3,000 people - Pope Francis emphasised on the importance of the plurality of faith. The prayer service on Friday (Sept 25) was attended by 700 people, including a dozen religious leaders from the Jewish, Muslim, Hindu, Sikh, Buddhist and Greek Orthodox traditions.

The Pope said Ground Zero "speaks so powerfully of the mystery of evil", adding:

"In opposing every attempt to create a rigid uniformity, we can and must build unity on the basis of our diversity of languages, cultures and religions."

5. On family

Pope Francis has mostly used his US trip to emphasise conservative values and Catholic teachings on the family. He pushed those two themes again at the star-studded Festival of Families event on Saturday (Sept 26), where actor Mark Wahlberg was the emcee and music legend Aretha Franklin serenaded the audience. The outdoor Catholic festival is a night of music and prayer held once every three years.

In an off-script speech laden with jokes, he described the family as "a factory of hope", each one with "divine citizenship" and charmed the crowd with remarks that have since taken off on social media:

"Families quarrel and sometimes plates can fly and children bring headaches, and I won't speak about mothers-in-law... But those difficulties are overcome with love."

6. Answering tough questions about God

At the Festival of Families event, the Pope also shared with the audience one of the tougher questions he has been asked. He said the query stumped him:

"A child once asked me - and you know that kids ask difficult questions - he asked me, 'Father, what did God do before he created the world?' I can assure you, I found it really hard to answer the question. So I said what I'm now going to say to you: Before creating the world, God loved."

7. Advice to inmates

On his Sunday (Sept 27) stop at Philadelphia's Curran-Fromhold Correctional Facility, which is the largest prison in the state, Francis had kind words for the inmates. He told them that their time of incarceration could have only one purpose - rehabilitation and paving their return to society:

"All of us are invited to encourage, help your rehabilitation. Life means 'getting our feet dirty' from the dust-filled roads of life and history. All of us need to be cleansed, to be washed, all of us and me in the first place."

8. On the sexual abuse scandal

The trip also saw the Pope offering his most comprehensive comments on the sexual abuse scandal since taking over the papacy in 2013. The remarks told to a group of bishops at St Charles Borromeo Seminary on Sunday (Sept 27) are believed to be the first time any pope has publicly described the abuse as rape.

Using his strongest language yet to condemn it, he promised that "all responsible will be held accountable". He told the victims he deeply regretted that some bishops had failed to protect children and was disturbed that in some cases, bishops were the abusers:

"I have in my heart the stories of suffering and the pain of the minors who were sexually abused by priests. This disgrace keeps burdening me, that the people who had the responsibility of caring for these tender ones raped them and caused them great pain. God weeps for the sexual abuse of children."

SOURCE: AFP, REUTERS, BLOOMBERG, NEW YORK TIMES, THE GUARDIAN