Receiving God's mercy ignites in us the drive to become "instruments of mercy," especially to the weakest and the marginalized, Pope Francis said Saturday at a vigil for the feast of Divine Mercy.

"The more we receive, the more we are called to share it with others; it cannot be kept hidden or kept only for ourselves," he said, addressing those gathered in St. Peter's Basilica. 

"It is something which burns within our hearts, driving us to love, thus recognizing the face of Jesus Christ, above all in those who are most distant, weak, alone, confused and marginalized."

Falling each year on the first Sunday after Easter, the feast of Divine Mercy was instituted by St. John Paul II in 2000 during the canonization of St. Faustina Kowalska, the Polish mystic whose apparitions of Jesus inspired devotion to the Divine Mercy.

This year's feast falls within the Jubilee Year of Mercy, which Pope Francis publicly proclaimed during the 2014 vigil for the feast of Divine Mercy. The Jubilee began Dec. 8, 2014, and will conclude Nov. 20.

"Mercy seeks out the lost sheep, and when one is found, a contagious joy overflows.  Mercy knows how to look into the eyes of every person; each one is precious, for each one is unique," the Pope said during his addess. 

Francis delivered his vigil address following a series of testimonies and readings from Scripture, all on the theme of mercy.

The expressions of God's mercy in His encounters with us are "numerous," he said; "it is impossible to describe them all, for the mercy of God continually increases."  

"God never tires of showing us mercy and we should never take for granted the opportunity to receive, seek and desire this mercy," he said.  

"It is something always new, which inspires awe and wonder as we see God's immense creativity in the ways he comes to meet us."

Throughout Scripture, God has frequently revealed himself as mercy, the Pope observed.

"How great and infinite is the nature of God, so great and infinite his mercy, to the point that it is greatly challenging to describe it in all its entirety."  

Francis cited a passage from the prophet Isaiah, and its "extremely evocative" image of God holding each of us to his cheek. 

He had this passage in mind for the image of the Jubilee, he said: "I led them with cords of compassion, with the bands of love, and I became to them as one who eases the yoke on their jaws, and I bent down to them and fed them" (Isaiah 11:4).  

"How much tenderness and love is expressed here!" the Pope said. "Jesus not only carries humanity on his shoulders, but his face is so closely joined to Adam's face that it gives the impression they are one."

Francis reflected on God's capability of "understanding and sharing our weaknesses" through Christ's Incarnation.

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"Precisely because of his mercy God became one of us," he said. 

By being touched by God's mercy in Jesus, moreover, we are in turn "inspired to become instruments of his mercy," the Pope continued.  

"It is easy to speak of mercy, yet more difficult to become its witness." 

He spoke of the many ways in which mercy comes to us: "closeness and tenderness," "compassion and solidarity," "consolation and forgiveness" – and this in turn compels us to share mercy with others, he said. 

Francis also reflected on how Christ's love "makes us restless" and "impels us to embrace, welcome and include those who need mercy, so that all may be reconciled with the Father."  

"We ought not to fear for it is a love which comes to us and involves us to such an extent that we go beyond ourselves, enabling us to see his face in our brothers and sisters," he said.  

"Let us allow ourselves to be humbly guided by this love; then we will become merciful as the Father is merciful."

In off-the-cuff remarks, Francis referenced the Gospel reading which recounts the Apostle Thomas' initial disbelief, and his need to place his fingers into Jesus' wounded side in order to be convinced of his resurrection. 

A faith that does not allow us to put our fingers into the wounds of Jesus' side "is not faith," the Pope said. "It is not a faith that is capable of being merciful."

"It is not faith. It is an idea. It is ideology. Our faith is incarnate, in a God who was made flesh," he said, "who was wounded for us." 

If we want to believe "with seriousness," the Pope said, "we must come close to and touch the wounds, caress the wounds," while bowing our heads to allow others to "caress our wounds."

The Pope concluded by urging faithful to remain open to being transformed by the Holy Spirit, who is the love and "mercy that is poured into our hearts."  

"May we not place obstacles to his life-giving work but with docility follow the path he shows us," he said.  

"Let us open our hearts so that the Spirit can transform us; thus forgiven and reconciled, we will become witnesses to the joy that brims over on finding the risen Lord, alive among us."