The message and devotion to Jesus as The Divine Mercy is based on the writings of Saint Faustina Kowalska.
The message of mercy is that God loves us — all of us — no matter how great our sins. He wants us to recognize that His mercy is greater than our sins, so that we will call upon Him with trust, receive His mercy, and let it flow through us to others. Thus, all will come to share His joy.
The Divine Mercy Devotion involves a total commitment to God as Mercy. It is a decision to trust completely in Him, to accept His mercy with thanksgiving, and to be merciful as He is merciful.
The devotional practices revealed through Saint Faustina were given to us as "vessels of mercy" through which God's love can be poured out upon the world, but they are not sufficient unto themselves. It's not enough for us to hang The Divine Mercy image in our homes, pray the Chaplet every day at three o'clock, and receive Holy Communion on the first Sunday after Easter. We also have to show mercy to our neighbours. Putting mercy into action is not an option of the Divine Mercy Devotion; it's a requirement!
How do we "radiate" God's mercy to others? By our actions, our words, and our prayers. "In these three degrees," he tells Sister Faustina, "is contained the fullness of mercy". The first: the act of mercy, of whatever kind. The second: the word of mercy-if I cannot carry out a work of mercy, I will assist by my words. The third: prayer-if I cannot show mercy by deeds or words, I can always do so by prayer. My prayer reaches out even there where I cannot reach out physically.