Speaking spontaneously to a group of Cuban nuns, priests, seminarians and bishops, the Pope said that Jesus shines in the lives of hidden and ignored people, such as those who suffer from degenerative diseases.
He also referred to prenatal testing that can forecast illnesses in the womb, leading some parents to "return it (the baby) before it comes into the world."
The Pope, who is in Cuba until Tuesday afternoon, said he wanted to speak off-the-cuff in response to two "prophets," who spoke before him Sunday evening. One was a nun who works with severely ill children.
Repeating a familiar theme, Francis also called for the church to embrace a "spirit of poverty," saying that "wealth takes away the best of us."
"Bad accountants are great for the church, because they make it free, make it poor," the Pope said. "God wants it to be poor ... . Blessed are the poor of the heart, those who aren't attached to money."
Later Sunday evening, under a drizzle of rain, Francis urged a crowd of young Cubans in Havana to "open yourself, and dream."
"Dream that if you give the best of yourself, you'll help make the world a different place."
While avoiding overtly political statements, the pontiff also repeated his frequent criticism of a "throwaway culture" and the "idolatry of money."
"Children aren't loved, they're killed before being born," he said. "The elderly are thrown away, because they don't produce. Some countries have euthanasia. But in some others there a hidden euthanasia. The youth is thrown away because they have no job opportunities."
In the prepared remarks that he did not deliver on Sunday but said will be published shortly, the Pope compared communities that don't argue to an old couple who have lost interest in each other.
"Conflicts and disagreements in the church are to be expected and, I would even say, needed," said the Pope. "They are a sign that the church is alive and that the spirit is still acting, still enlivening her."
Such sentiments are a sharp break from Francis' papal predecessors -- Saint John Paul II and Benedict XVI -- both of whom discouraged dissent within the church.
Francis' comments come as the Catholic Church is holding a fierce debate over several controversial issues, including whether divorced and remarried Catholics should be able to receive Communion. Earlier this month, Francis made it easier and cheaper for Catholics to annul their marriages
, leading some American conservatives to accuse him of "vandalizing" the sacrament
In October, the Vatican will host a large meeting of top bishops to discuss challenges facing modern families, including annulments, and outreach to gays and lesbians.
Earlier on Sunday, Pope Francis met briefly with former Cuban President Fidel Castro, then held a longer meeting with his brother, current President Raul Castro.
On Tuesday, Francis will fly to Washington, the first stop on his three-city trip to the United States. In a prominent sign of the disagreements among American Catholics, Rep. Paul Gosar, a Republican -- and Catholic -- from Arizona, said he plans to boycott the Pope's speech
"When the Pope chooses to act and talk like a leftist politician," Gosar said, "then he can expect to be treated like one."
Other Catholic politicians, such as New Jersey Gov. Chris Christie, who is running for president, said the Pope was wrong
to help broker a diplomatic detente between the United States and Cuba.
"The fact is that his infallibility is on religious matters, not on political ones," Christie told CNN's Jake Tapper.