On Thursday Pope Francis will become the first Bishop of Rome to address a joint session of the US Senate and House of Representatives. During his speech he will tackle the misinterpretation of his words on economics and politics.

That expectation is according to a source who saw the first drafts of the speech, and who spoke with CNA Sept. 18.

"Pope Francis will likely use the speech to Congress to clarify his position on economics and politics, thus indirectly responding to the misinterpretation of his words," the source maintained.

According to the source, the speech will also include a mention of the market: "Pope Francis will clarify that he never said he wants to abolish the market, but that he said the market needs a purification."

The American audience made much of Pope Francis' criticism of capitalist systems which he made during his South American trip this summer.

During a July 9 address at the World Meeting of Popular Movements in Santa Cruz de la Sierra, Bolivia, he said that "the stench of what Basil of Caesarea – one of the first theologians of the Church – called 'the dung of the devil'" lies behind global capitalism's indifference to the poor and the planet."

"An unfettered pursuit of money rules," the Pope continued. "This is the 'dung of the devil' … Once capital becomes an idol and guides people's decisions, once greed for money presides over the entire socioeconomic system, it ruins society, it condemns and enslaves men and women, it destroys human fraternity, it sets people against one another and, as we clearly see, it even puts at risk our common home, sister and mother earth."

Pope Francis added that "in this subtle dictatorship" capital has become and idol, and called for a "real change, structural change" to solve the situation.

However, his speech to Congress will be addressed particularly to the American audience – and it will not be linked to his speech the following day to the United Nations in New York, the source maintained.

Migration will also likely be a core issue in the papal speech, with the Pope would praising the United States for their multicultural composition, while also calling for a wider welcoming of immigrants.

"Pope Francis has already given a sign of what he would like the US to do in terms of immigration. When he took part to the ABC show 20/20, he directly addressed Sr. Norma Pimentel, the director of Catholic Charities in Rio Grande, who manages a welcoming center for immigrants who are left at the border. That's the kind of welcoming he thinks about," the source maintained.

Unfortunately, not every congressman will hear the Pope's message.

Rep. Paul Gosar (R-Ariz.) – who is himself Catholic – announced on Friday that he would boycott Pope Francis' speech, in protest of the Roman Pontiff's views on climate change.

Gosar claimed that he would be joined in his protest by at least one other legislator, while declining to name that person.

Other lawmakers are more open to lending an ear to the Pope.

Rep. Carlos Curbelo (R-Fla.), said, "I'm sure I'll disagree with something the Pope says," according to The Hill. "But I still embrace my religion. It's literally a once-in-a-lifetime opportunity to sit here and listen to the Holy Father."

And Marco Rubio, a Florida Senator of Cuban descent who is running for the Republican nomination for United States President, wrote in an opinion piece at CNN that he hopes the Pope's visit to Cuba "will remind all the Cuban citizens that they possess dignity and fundamental rights that come from God and that the Castro regime has no claim on changing what is 100% God-given."

Rubio had contrasted the state of freedoms – religious and otherwise – enjoyed by citizens of the United State and of Cuba.

"I pray the Pope can use his moral authority to inspire true religious freedom, and bring us closer to the day when freedom can finally take root on the island country; because only then will the people of Cuba prosper and have the opportunity to live out God's plan," he wrote.

"Please join me in welcoming Pope Francis to the United States, and helping him to spread peace and prosperity to people around the world."