Pope Francis is welcomed in Cuba. (Courtesy of CNA)

HAVANA, CUBA (CNA/EWTN News) - Pope Francis on Sunday spoke from the heart about the importance of spiritual poverty, the danger of worldly wealth, and the universal need for mercy. He made his impromptu remarks to Cuban priests, consecrated religious and seminarians at Havana's cathedral.

"The spirit of the world does not love the way of the Son of God, who emptied himself and became poor. He became nothing - he humiliated himself in order to be one of us," the Pope said, adding that every individual is called to this same poverty.

Pope Francis talked about the "things of the heart" and the Christian duty to welcome poverty and not hide from it. He had set aside his prepared homily for evening prayer at the Cathedral of the Virgin Mary of the Immaculate Conception Sept. 20.

Many generous souls fall away from the faith because they are enraptured by the mundane, by the worldly, and by the mediocre, he continued. He warned those gathered to stay away from the temptation of worldly riches.

"Richness impoverishes you in a bad way--it takes the best we have and makes us poor," the Pope asserted. He contrasted this with spiritual wealth, saying that "to be rich is to trust in God."

The Pope encouraged all consecrated religious to "love poverty as a mother." He advised them to look interiorly at themselves and ask: "How is my spirit of poverty? How is my interior detachment?"

He also drew on his background with the Society of Jesus and its founder, St. Ignatius of Loyola.

"I think it can be helpful to you to hear what St. Ignatius told us - and this is not an advertisement!" he joked about his Jesuit past.

"Poverty is the wall and the mother of consecrated life. It is the mother because it engendered trust in God, and it is the wall because it protected it from any mundane affections," the Pope explained.

He went on to talk about how to treat the "littlest ones" in the world, because this is the standard by which Christians will be judged.

"Who is the least one? Where do I find him?" the Pope asked.

He explained that the "least of my brothers" are the forsaken and the last in the world, the ones whom the world despises and hides away. From them, "the smile of a person who is paralyzed," or even a "drooling kiss" can show the tenderness and mercy of God, he stated.

Turning to priests, the Pope noted a privileged place where the clergy can find and meet the forsaken and the least of the world: the confessional.

The confessional is "where the least one appears, where that man or woman shows their misery to you."

Pope Francis asked priests everywhere not to chastise or punish those who go to confession; rather, Pope Francis encouraged clergy to show them the mercy of God.

"Do not grow tired of forgiving. Be forgivers. When the penitent come to you, do not drive them away from the confessional. Jesus embraced them. Jesus loved them," he continued.

"Do not be afraid of the mercy of God. Let it flow through your hands and through your forgiving embrace, because that man or woman is the least, and therefore, they are Jesus," Pope Francis urged.

The Holy Father ended his off-the-cuff remarks with a prayer that asked God for the gift to be poor in spirit and to be merciful: "May the Lord give us these graces: poverty and mercy, because there, we find Jesus."

Before the Pope spoke, Cardinal Jaime Ortega of Havana asked the Pope to bless the Church in Cuba. A religious sister spoke to the Pope and reflected on her experience when she found out her community assigned her to care for people with disabilities. She said she thought it would be the most demanding of her assignments.

But the greatest demand was to follow Christ, she said.

"You learn to be the mother of the poor," she said. "We trust in the guidance of Jesus, the Good Shepherd, and Mary, our Mother."

Pope Francis has spent a full day in Cuba. He celebrated Mass outside in Havana for an estimated 200,000 people and briefly met with the former president, Fidel Castro. The pontiff's trip to Cuba will last until Tuesday, after which he will travel to the United States.