3. The Rosary shall be a powerful armor against hell, it will destroy vice, decrease sin and defeat heresies.
This promise, along with the next, is simply the reminder on how fervent prayer will help us all grow in holiness by avoiding sin, especially a prayer with the excellence of the Rosary. An increase in holiness necessarily requires a reduction in sin, vice, and doctrinal errors (heresies). If only the Modernists could be convinced to pray the Rosary! St. Louis de Montfort states “Since Mary alone crushed all heresies, as we are told by the Church under the guidance of the Holy Spirit (Office of the Blessed Virgin Mary)…” [True Devotion to Mary #167]