One of the people who gave testimony was Manuel, a teenager in a wheelchair who suffers from muscular dystrophy.
The Pope responded to Manuel by name, acknowledging how he had put his "heart" into his life, his family, and his friendships.
"I believe that this is what the Holy Spirit always wants to do in our midst: to put a new heart into us, giving us reasons to keep on taking risks, dreaming and building a life that has this sense of home, of family."
"This is something which God the Father has always dreamt of and for which he has fought for a very long time."
The Pope reflected on examples throughout Scripture in which God placed a "new heart" into the people: he assured Adam and Eve in the Garden of Eden that all was not lost; he gave manna to the people of Israel as they journeyed through the desert.
Finally, "when the fullness of time came, God the Father put his heart into it by giving humanity the eternal gift of his Son."
"Similarly, all of us here have had this experience, in different moments and different ways; God the Father has put his heart into it for us," the Pope said.
God "cannot do otherwise," he said: "Because his name is love, his name is gift, his name is self-giving, his name is mercy."
This is shown in his Son, Jesus, in whom and with whom the "Kingdom of God" possible.
(Story continues below)
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This Kingdom, the Pope said, "invites us to share in a new mindset, that puts into motion a dynamic power capable of opening the heavens, capable of opening our hearts, our minds, our hands and capable of challenging us with new possibilities."
"This is a Kingdom which has the feeling of family, the flavor of a life shared."
Jesus "is capable of changing our perspectives, attitudes, and feelings, which are often watery and dull, into the wine of joy and celebration," the Pope continued.
"He can heal our hearts and invite us again and again, seventy times seven, to begin anew. He can make all things new."
Pope Francis responded to Manuel's request for prayers for those adolescents who are disillusioned and "on a wrong path," many of whom "are deflated, tired and without aspirations."
"This attitude often comes from a feeling of loneliness, from not having someone to talk to," the Pope said.