Some years after her (Mary’s) death, whiles St. John the Evangelist was grieving over his loss and longing to see her face again, it pleased our Blessed Lord to appear to him in a vision, accompanied by His Mother. The sorrows of Mary, together with her frequent visits to the holy places of the Passion, were naturally a constant subject of devout contemplation to the Evangelist, who had watched over the last fifteen years of her life; and, as if it were in response to these continual meditations, he heard her ask Jesus to grant some special favor to those who should keep her dolors in remembrance. Our Lord replied that He would grant four particular graces to all those who should practice this devotion. The first was a perfect contrition of all their sins some time before their death; the second was a particular protection in the hour of death; the third was to have the mysteries of the Passion deeply imprinted in their minds; and the fourth a particular power of impetration granted to Mary’s prayers on their behalf.
Foot of the Cross, Faber, page 81