Excerpts from St. Faustina's Diary
In the evening, when I was in my cell, I saw the Lord Jesus clothed in a white garment. One hand [was] raised in the gesture of blessing, the other was touching the garment at the breast. From beneath the garment, slightly drawn aside at the breast, there were emanating two large rays, one red, the other pale. In silence I kept my gaze fixed on the Lord; my soul was struck with awe, but also with great joy. After a while, Jesus said to me, 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 am offering people a vessel with which they are to keep coming for graces to the fountain of mercy. That vessel is this image. ... By means of this image I will grant many graces to souls. (Diary, entries 47-48, 327 and 742)