God the Father gave his only Son to the world only through Mary.
Whatever desires the patriarchs may have cherished, whatever entreaties the prophets and saints of the Old Law may have had for 4,000 years to obtain that treasure, it was Mary alone who merited it and found grace before God by the power of her prayers and the perfection of her virtues.
"The world being unworthy," said Saint Augustine, "to receive the Son of God directly from the hands of the Father, He gave His Son to Mary for the world to receive Him from her."
The Son of God became man for our salvation but only in Mary and through Mary.
God the Holy Spirit formed Jesus Christ in Mary but only after having asked her consent through one of the chief ministers of His court.
St. Louis-Marie Grignion de Montfort, True Devotion to the Blessed Virgin