In the 40-minute-long conference, the Pope also spoke about the crisis in Venezuela, corruption, climate change and whether Colombia could provide a model for the peace process for other countries. He came forth about the situation a couple of times.
The Argentine pope, 80, held the last in a series of open-air masses in the Caribbean city of Cartagena-one of Colombia's top tourist draws but also one of its poorest cities.
In his homily in Medellin, Pope Francis said that when Jesus's disciples first began following him, they had to go through a process of conversion and purification, changing the way they saw the relationship between Jewish law and faith in God. "I express my closeness to each one of the sons and daughters of that beloved nation, as well as those who have found refuge on this Colombian soil".
The pope has been an ardent supporter of efforts to combat climate change and its consequences to the world's most vulnerable populations, in terms of pollution, disease, wars and migration.
His last day in the Andean country got off to a rocky start when he lost his balance and bumped his head while riding in the popemobile.
"We are called upon to be fearless, to have that evangelical courage which springs from knowing that there are many who are hungry, who hunger for God, who hunger for dignity, because they have been deprived", the Pope said.
Everyone has a moral responsibility to act, he said.
"This holy blood is staying in Colombia", said Ricardo Morales, a lawyer who lined up outside St. Peter Claver's church for a glimpse of the pope.
In Cartagena, he visited the impoverished district of San Francisco, where he blessed the foundations of a new homeless shelter. "A phrase from the Old Testament comes to me, from the Psalm: "Man is stupid".
"Here, there are lots of people who only eat once a day".
The Medellin that Francis visited is a city transformed since his predecessor Pope John Paul visited in 1986. "The worst thing is the corruption - that is worse than the bullets of the guerrillas or the paramilitaries".
"Those who are abandoned, immigrants and those who suffer violence and human trafficking".
He was standing up in the specially designed vehicle, waving to admirers, when it braked sharply and he collided with the glass.
After he was assisted from the auto, he was then seen with a black eye and and a small dressing on his brow. "I believe it is not something to joke around with".