On the first Sunday of Lent, February 22, 1931, Our Lord Jesus Christ is reported to have granted a vision of Himself to St. Maria Faustina Kowalska of the Congregation of Sisters of Our Lady of Mercy in the city of Plock in Poland.
She saw Him clothed in an ankle-length white garment, His right hand was raised in blessing: the left was touching His garment at the breast where, from beneath the garment lightly drawn aside, two large rays were coming forth as though from His heart. The ray to the left of the onlooker was red in color; the ray to the right was pale, that is colorless, like a clear crystal.
After St. Faustina had gazed intently at the vision for a while with emotions of deep reverence and great joy, Jesus gave her these instructions:
Paint an image according to the pattern you see, with the signature: Jesus, I trust in You! I desire that this image be venerated, first in your chapel, and then throughout the world. I promise that the soul that will venerate this image will not perish. I also promise victory over enemies already here on earth, especially at the hour of death. I Myself will defend it as My own glory.
Upon the request of her spiritual director, St. Faustina asked whether the words "Christ, the King of Mercy" could be the inscription on the image. Jesus gave her this answer: I am the King of Mercy. I desire that this image be displayed in public on the first Sunday after Easter. That Sunday is the Feast of Mercy. St. Faustina then heard these words coming from God the Father: Through the Word Incarnate I make known the bottomless depth of My mercy.
Further, in prayer she received the inner understanding that these words must be clearly in evidence on the image: "Jesus, I trust in You."
When her spiritual director asked about the meaning of the rays, she received this explanation from the Lord: 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 very 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.