DEAR MINISTERS of the Most High, you my fellow priests who preach the truth of God and who teach the gospel to all nations, let me give you this little book as a white rose that I would like you to keep. The truths contained in it are set forth in a very simple and straightforward manner as you will see. Please keep them in your heart so WHITE ROSE BUD that you yourselves may make a practice of the Holy Rosary and taste its fruit; and please have them always on your lips too so that you will always preach the Rosary and thus convert others by teaching them the excellence of this holy devotion.
I beg of you to beware of thinking of the Rosary as something of little importance----as do ignorant people and even several great but proud scholars. Far from being insignificant, the Rosary is a priceless treasure which is inspired by God.
Almighty God has given it to you because He wants you to use it as a means to convert the most hardened sinners and the most obstinate heretics. He has attached to it grace in this life and glory in the next. The Saints have said it faithfully and the Popes have endorsed it.
When the Holy Spirit has revealed this secret to a priest and director of souls, how blessed is that priest! For the vast majority of people fail to know this secret or else only know it superficially. If such a priest really understands this secret he will say the Rosary every day and will encourage others to say it. God and His Blessed Mother will pour abundant grace into his soul, so that he may become God's instrument for His glory; and his word, though simple, will do more good in one month than that of other preachers in several years.
Therefore, my dear brethren and fellow priests, it will not be enough for us to preach this devotion to others; we must practise it ourselves. Even if we firmly believed in the importance of the Holy Rosary but never said it ourselves, people could hardly be expected to act upon our advice, for no one can give what he does not have: "Jesus began to do and to teach." (Acts 1:1) We ought to pattern ourselves on Our Blessed Lord, Who began by practising what He preached. We ought to emulate Saint Paul who knew and preached nothing but Jesus Crucified. This is really and truly what you will be doing if you preach the Holy Rosary. It is not just a conglomeration of Our Fathers and Hail Marys, but on the contrary it is a Divine summary of the mysteries of the life, passion, death and glory of Jesus and Mary.
I could tell you at great length of the grace God gave me to know by experience the effectiveness of the preaching of the Holy Rosary and of how I have seen, with my own eyes, the most wonderful conversions it has brought about. I would gladly tell you all these things if I thought that it would move you to preach this beautiful devotion, in spite of the fact that priests are not in the habit of doing so these days. But instead of all this I think it will be quite enough for this little summary that I am writing if I tell you a few ancient but authentic stories about the Holy Rosary. These excerpts really go to prove what I have outlined for the faithful in French.
St. Louis-Marie Grignon de Montfort's The Secret of the Rosary