Promote the Practice of the Three Hail Marys Morning and Night
St. Mechtilde of Hackeborn lived in the Thirteenth century and was the novice mistress of St. Gertrude the great -- one of the first great Mystics of the Sacred Heart of Jesus. Once, St. Mechtilde beseeched Our Lady for her special help at the hour of death. Our Lady answered; "Yes, I promise you that; but you must recite each day three Hail Marys.
By the first, address yourself to God the Father, who in His sovereign power, exalted my soul... and ask Him that I be present at the hour of your death to comfort you and to chase away all the powers of the enemy.
By the second, address your self to God the Son, who in His unsearchable Wisdom, endowed Me with such knowledge and understanding as to unable me to enjoy the most Holy Trinity by the knowledge superior to that of all the other Saints. you will also ask Him... to fill your soul, at the hour of death, with lights of faith and knowledge, protecting you from all ignorance and error.
By the third, address yourself to God the Holy Ghost, who inundated me with his love... and you will ask Him that I be present at the hour of your death, to pour out on you the sweetness of Divine love. Thus you will triumph over the sorrows and the bitterness of death, until you see them transformed into the sweetness of every joy."
Other Saints
St. Anthony also preached the devotion of the Three Hail Marys, encouraging souls to say it in honour of Mary's Immaculate purity.
St. Leonard of Port Maurice did the same, adding that it should be said morning and night, to avoid all mortal sins.
But St. Alphonsus Ligouri gave the greatest encouragement to this devotion in The Glories of Mary. Following him Redemptorist Missionaries often concluded their Missions encouraging souls to pray the Three Hail Marys for the grace of Purity, a good confession, and the help of Mary at the hour of death.
Source: Knight of the Immaculata