Saint Mechtilde of Hackeborn (1241-1299), a Benedictine nun from the monastery of Helfta (Germany), received three visions of the Virgin Mary. Concerned for her eternal salvation, she begged the Virgin to be present at the hour of her death.
During these apparitions, Mary reassured her and taught her how to recite three "Hail Marys" in honor of the three Persons of the Holy Trinity. The first to recall her power of intercession on behalf of sinners, which she received from the Eternal Father; the second for the wisdom she received from the Son; and the third, for the immense reservoir of love she holds inside her, since she is filled with the Holy Spirit.
According to Saint Gertrude the Great (1256-1301), the Blessed Virgin Mary promised this: ''To every soul who faithfully prays the Three Hail Marys, I will present myself at the hour of death in splendor so extraordinarily beautiful that it will fill his soul with celestial consolation.''