The prayer that will not fail
Around the year 1200, it is said that the Virgin Mary appeared to St. Dominic and told him to “Pray my Psalter and teach it to your people. That prayer will never fail”. Dominic did spread devotion to the Psalter of Mary, and as Father Richter stated, the devotion was “divinely incorporated in the personal vocation of St. Dominic.”
Over the next decades, the Rosary and the Psalter of Mary converge, and the devotion takes the specific form that we know today the 150 Hail Marys are divided into decades, an Our Father is inserted between them, and the three sets of mysteries Joyful, Sorrowful and Glorious are established.