Vatican City, May 19, 2016 / 04:07 pm (CNA/EWTN News).- During his Mass on Thursday, Pope Francis preached a warning to the rich who oppress the poor, focusing on employers who accumulate wealth by misusing those who work for them.

“We consider this drama of today: the exploitation of the people, the blood of these people who become slaves, the traffickers of people – and not just those who deal in prostitutes and children for child labour,” Pope Francis said May 19 during his Mass in the chapel of Santa Marta House in the Vatican.

In addition, he said, there is a “more – so to speak – 'civilized'” form of trafficking which happens when an employer says, “I’ll pay you this much, without vacation, without health care, … everything under the table… But I will become rich!”

The Pope's homily was based on the Epistle of James, which told of woe for the rich who oppress the poor. Calling the passage “a little strong,” he said St. James clearly “understood the danger there is when a Christian allows himself to be controlled by wealth.”

Riches, Pope Francis said, “in and of themselves are good things,” and noted that there are “many righteous rich men” in the Bible, including Job and Tobias. However, he added, riches are a “relative, not absolute” good, and the Lord commended Solomon “for asking not for wealth but for wisdom of heart.”

In themselves, riches “are good; but if you prefer to serve God, riches come in second place – the right place,” he said.

Pope Francis recalled the rich young man in the Gospel, saying that he “was good, but attached to riches, and these riches in the end became for him the chains that took away his freedom to follow Jesus.”

He criticized the “theology of prosperity,” according to which “God shows you that you are just if he give you great riches,” calling it mistaken.

The Pope offered these questions as a way to examine one's conscience with regard to wealth: “Is my heart set on riches or is it not? What is my relationship with wealth?”

He said St. James' warning to the rich was aimed especially at those whose “wealth is made by exploiting people … those rich people who exploit [others], they take advantage of the work of the people, and those poor people become slaves.”

Giving a contemporary example, he pointed to those who are given only seasonal work, “with no opportunity for a pension, without health insurance.” Employers who do this “are true leeches and they live by spilling the blood of the people whom they make slaves of labour.”

He also pointed to a woman who was offered a job working 11-hour days for less than $730 a month, all under the table. When she balked, he said, she was told: “Look at the line behind you. If you want it, take it, if no, leave. There are others waiting.”

Such employers “fatten themselves on wealth,” Pope Francis said, adding that contemporary exploitation of workers “is truly a form of slavery.”

“We used to think that slaves no longer exist: they exist. It’s true, people are not going and taking them from Africa to sell them in America, no. But it is in our cities.”

Such employers are traffickers and “do not realize it,” he said.

“The blood you have sucked from of all these people … is a cry to the Lord, it is a cry for justice.”

The Pope also referred to Christ's story of The Rich Man and Lazarus, saying the rich man “was in his own world; he did not notice that on the other side of the door to his house was someone who was starving. But this is worse. That rich man at least did not realize, and left the other man to die of hunger. But this is worse. This is starving the people with their work for my own profit! Living on the blood of the people. And this is a mortal sin. This is a mortal sin. It requires a great deal of penance, a great deal of restitution, in order to be converted from this sin.”

Pope Francis concluded his homily by asking that that the Lord might “make us understand today the simplicity that Jesus speaks to us of in today's Gospel: a glass of water in the name of Christ is more important than all the riches accumulated through the exploitation of the people.”