As Pope Francis blessed children's nativity scene figurines Sunday, the pope said that the Advent season is a time of conversion to make space in one's heart for Christ to come and fill it with joy.

"Advent, a time of grace, tells us that it is not enough to believe in God: it is necessary to purify our faith every day," Pope Francis said in his Angelus address Dec. 15.

"It is a matter of preparing to welcome -- not a fairy-tale character -- but the God who calls us, involves us, and before whom a choice is imposed," he said in St. Peter's Square.

Italian children gathered in St. Peter's Square before the Angelus prayer, shouted and cheered as they awaited the papal blessing of their Nativity scene figurines of the infant Jesus, called "Bambinelli" in Italian.

This 50 year-old Vatican tradition of the blessing the infant Jesus figurines on Gaudete Sunday began in 1969 with St. Pope Paul VI at the iniative of the Roman Oratori Center. The tradition has since spread throughout the world each year on the third Sunday of Advent.

"I greet you, dear children, who have come with the statues of the child Jesus for your nativity scenes. I cordially bless you," Francis said.

Pope Francis reminded the children of the meaning of the nativity scene by quoting a passage of his apostolic letter, Admirabile Signum, published on the first day of Advent this year:

"The nativity scene is like a living Gospel," he said. "As we contemplate the Christmas story, we are invited to set out on a spiritual journey, drawn by the humility of the God who became man in order to encounter every man and woman. We come to realize that so great is his love for us that he became one of us, so that we in turn might become one with him."

The pope said that the child Jesus in the nativity scene has "the face of our most needy brothers and sisters."

"The poor are a privileged part of this mystery; often they are the first to recognize God's presence in our midst," he said.

The time of Advent reminds us that joy and doubt are both experiences that are a part of life, the pope said.

"But the man of God looks beyond, because the Holy Spirit makes his heart feel the power of his promise, and he announces salvation: 'Courage, do not fear! Behold your God ... He comes to save you,'"  Pope Francis said.

"And then everything is transformed: the desert blooms, consolation and joy take possession of fearful hearts, the lame, the blind, the mute are healed. This is what is accomplished with Jesus: 'the blind regain their sight, the lame walk, the lepers are purified, the deaf hear, the dead rise, the Gospel is announced to the poor,'" he said quoting the Gospel of Matthew.

This description from Matthew's Gospel shows that "salvation envelops the whole man and regenerates him," the pope said. "But this new birth, with the joy that accompanies it, always presupposes a dying to ourselves and to the sin that is in us."

"Hence the call to conversion, which is the basis of the preaching of both the Baptist and Jesus; in particular, it is a question of converting the idea we have of God. And the time of Advent encourages us to do so," he said.

Pope Francis reminded the crowd that the Christmas novena will begin Dec. 16. He also asked for prayers for the fruitfulness of the International Eucharistic Congress to be held in Budapest, Hungary in September 2020.

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"May the Virgin Mary help us as we approach Christmas, not to allow ourselves to be distracted by external things, but make space in our heart for Him who has already come and wants to come again to heal our illnesses and give us his joy," Pope Francis said.