Pope Francis is wrapping up his Colombia trip with a deeply personal final day honoring St. Peter Claver, a fellow Jesuit who ministered to thousands of African slaves who passed through the port of Cartagena during Spanish colonial times.

Claver, the self-described "slave of the slaves forever," has been revered by Jesuits, popes and human rights campaigners for centuries for having insisted on recognizing the dignity of slaves when others treated them as mere merchandise to be bought and sold.

On the eve of his visit to Cartagena, Francis celebrated Claver's feast day by praising the 17th century Spanish missionary for having "understood, as a disciple of Jesus, that he could not remain indifferent to the suffering of the most helpless and mistreated of his time, and that he had to do something to alleviate their suffering."

History's first Latin American pope has similarly insisted on ministering to society's most marginal and making them the focus of the Catholic Church's mission. He takes special care of the homeless who live around the Vatican, makes regular phone calls to prisoners, brought a dozen Syrian refugees home with him from a Greek refugee camp, and embraces the sick, the maimed and the deformed every chance he gets.

He is to pray at Claver's tomb on Sunday after laying the foundation for new residences for homeless people in Cartagena, the city famous for its UNESCO-awarded historic center but also home to slums and shanties.

Francis is likely to hold Claver up as a model for today's Catholic Church, someone who insisted on recognizing the inherent human rights of everyone. It's a message he referenced in Medellin on Saturday during a Mass on a rain-soaked airport tarmac that drew upward of 1 million people. Francis demanded that his church not hold fast to rigid doctrine but instead seek out the sinners and outcasts and welcome them in.

"My brothers, the church is not a customs post," Francis said. "It wants its doors to be open."

Francis returns to Rome from Cartagena on Sunday night, ending a five-day visit highlighted by a huge prayer of reconciliation that brought together victims of Colombia's long-running conflict and demobilized guerrillas and paramilitary fighters.

While in Colombia, Francis refrained from making any public comments about the deteriorating political and humanitarian situation next door in Venezuela, though he did meet briefly with a delegation of Venezuelan bishops. He will most certainly be asked about it during his airborne press conference en route home.