In Mary, God has given us the most zealous guardian of Christian unity. There are, of course, more ways than one to win her protection by prayer, but as for us, We think the best and most effective way to her favor lies in the Rosary.
. . . When such faith is exercised by vocally repeating the Our Father and Hail Mary of the Rosary prayers, or better still in the contemplation of the mysteries, it is evident how close we are brought to Mary. For every time we devoutly say the Rosary in supplication before her, we are once more brought face to face with the marvel of our salvation; we watch the mysteries of our redemption as though they were unfolding before our eyes; and as one follows another, Mary stands revealed at once as God's Mother and our Mother.
. . . Meditation on the mysteries of the Rosary, often repeated in the spirit of faith, cannot help but please her and move her, the fondest of mothers, to show mercy to her children.
For that reason We say that the Rosary is by far the best prayer by which to plead before her the cause of our separated brethren. To grant a favorable hearing belongs properly to her office of spiritual Mother. For Mary has not brought forth -- nor could she -- those who are of Christ except in the one same Faith and in the one same love; for "Can Christ be divided?
Pope Leo XIII
Encyclical Adiutricem, September 9, 1895