In 1931, our Lord appeared to St. Faustina and she recorded the following:
Paint an image according to the pattern you see, with the signature: Jesus, I trust in You. I promise that the soul that will venerate this image will not perish. I also promise victory over [its] enemies already here on earth, especially at the hour of death. I Myself will defend it as My own glory (Diary, 47, 48).
I am offering people a vessel with which they are to keep coming for graces to the fountain of mercy. That vessel is this image with the signature: Jesus, I trust in You (327). I desire that this image be venerated, first in your chapel, and [then] throughout the world (47).
At the request of her spiritual director, St. Faustina asked the Lord about the meaning of the rays in the image. She heard these words in reply:
The two rays denote Blood and Water. The pale ray stands for the Water which makes souls righteous. The red ray stands for the Blood which is the life of souls. These two rays issued forth from the depths of My tender mercy when My agonized Heart was opened by a lance on the Cross. Happy is the one who will dwell in their shelter, for the just hand of God shall not lay hold of him (299). By means of this image I shall grant many graces to souls. It is to be a reminder of the demands of My mercy, because even the strongest faith is of no avail without works (742).
These words indicate that the Image represents the graces of Divine Mercy poured out upon the world, especially through Baptism and the Eucharist. Many different versions of this image have been painted, but our Lord made it clear that the painting itself is not what is important. When Faustina first saw the original image that was being painted under her direction, she wept in disappointment and complained to Jesus: “Who will paint You as beautiful as You are?” (313). In answer, she heard these words: “Not in the beauty of the color, nor of the brush lies the greatness of this image, but in My grace” (313). No matter which version of the image we prefer, we can be assured that it is a vehicle of God’s grace if it is revered with trust in His mercy.This devotion comes with a beautiful chaplet, novena, and prayer at three in the afternoon. All is meant to be a vehicle to God’s mercy for all humanity.
Here’s a clip for your listening enjoyment on mercy. Miserere by Gregorio Allegri.