The Mystical City of God by Venerable Mary of Agreda
"I have not revealed these mysteries in the primitive Church, because they are so great, that the faithful would have been lost in the contemplation and admiration of them at a time when it was more necessary to establish firmly the law of grace and of the Gospel. Although all mysteries of religion are in perfect harmony with each other, yet human ignorance might have suffered recoil and doubt at their magnitude, when faith in the Incarnation and Redemption and the precepts of the new law of the Gospel were yet in their beginnings.
On this same account the person of the incarnate Word said to his disciples at the last supper: "Many things have I to say to you; but you are not yet disposed to recieve them" (John 6, 12). These words He addressed to all the world, for it was not yet capable of giving full obedience to the law of grace and full assent to the faith in the Son, much less was it prepared to be introduced into the mysteries of his Mother. But now, mankind has greater need for this manifestation, and this necessity urges Me to disregard their evil disposition. And if men would now seek to please Me by reverencing, by living, and studying the wonders, which are intimately connected with this Mother of Piety, and if they would all begin to solicit her intercession from their whole heart, the world would find some relief. I will not longer withhold from men this mystical City of refuge; describe and delineate it to them, as far as thy shortcomings allow. I do not intend that thy descriptions and declarations of the life of the Blessed Virgin shall be mere opinions or contemplations, but reliable truth. They that have ears to hear, let them hear. Let those who thirst come to the living waters and leave the dried-out cisterns; let those that are seeking for the light, follow it to the end. Thus speaks the Lord God Almighty!" (Vo1 1., The Mystical City of God: Life of the Virgin Mother of God, manifested to Sister Mary of Jesus of Agreda)