The Immaculate Conception of the Blessed Virgin Mary
The virtue and the greatness of the blessed and glorious Mary ever Virgin were proclaimed in Gods own words by the Angel when he said, Hail, full of grace, the Lord is with You. Blessed are You among women. For it was fitting that the Virgin should be enriched by gifts so great as to make Her full of grace She who gave glory to Heaven, the Lord to the earth, poured out peace on the world, gave faith to the nations, made an end to wickedness, brought order to life, instruction and discipline to human ways.
And indeed She is full of grace, for whereas grace is given to others only in part, on Mary it was poured out all at once in all its fullness. She is truly full of grace; for, even though, as we believe, the Holy Prophets and Fathers possessed grace, it was not yet in fullness; but into Mary came the whole fullness of all grace, which is in Christ, although in another way. And therefore the Angel says, Blessed are You among women, that is, more blessed than all other women.
Thus whatever curse devolved upon mankind through Eve was wholly removed by the blessing given to Mary. In Marys praise, as it were, Solomon says in the Canticle, Come, My dove, My immaculate one. For see, the winter is past, the rains are over and gone. And then he says, Come from Lebanon, come and be crowned.
Not without reason is She called to come from Lebanon. For the name Lebanon is interpreted shining whiteness. And Mary shines with the purity of many virtues, glistening whiter than the whitest snow with gifts of the Holy Spirit, in all things showing the simplicity of a dove. For everything about Her is wholly the work of purity and simplicity, of grace and truth, of the mercy and justice that look down from Heaven. And so She is unstained, since She is in no way corrupted.
She has encompassed a man in Her womb, as Holy Jeremias testifies, and received Him from no one else. The Lord, he says, will bring about a new thing upon the earth: a woman will encompass a man. Indeed this was a new thing, a work of power of a supereminent newness, when God (whom the world cannot contain, whom no man can see and live) so entered the guesthouse of Her womb as not to know confinement in Her body; and when He was so carried that the whole God was in Her womb; and He so came forth from it that (as Ezechiel prophesied) it was a door never opened. This is why the same Canticle sings of Her, A garden enclosed, a fountain sealed, your streams are those of paradise. Truly She is a garden of delights, planted with all kinds of flowers and the perfumes of all virtues; She is enclosed in that She has known no violation nor corruption by any wiles or deceits. She is a fountain sealed with the seal of the whole Trinity.From the Acts of Pope Pius IX
In answer to the petitions of the whole Church, Pope Pius IX decided solemnly to proclaim by his supreme and infallible pronouncement the victory of the Virgin Mother of God in Her Conception over the dreadful enemy of the human race a doctrine wonderfully set forth in Holy Scripture, in the venerable tradition and continuing consensus of the Church, as also in the common agreement of all bishops and faithful, and in outstanding acts and constitutions of the Holy See.
And therefore, on December 8, 1854, in the Vatican Basilica, in the presence of a vast assembly of Fathers of the Roman Church, including Cardinals and bishops from the most distant countries, and with the applause of the whole world, he solemnly declared and defined: The doctrine which holds that the Most Blessed Virgin Mary, at the first instant of Her conception, by a singular privilege granted Her by God, was preserved from any stain of original sin, is a doctrine taught and revealed by God, and is therefore to be believed with firmness and constancy by all the faithful.
Taken from The Hours of the Divine Office in English and Latin, Vol. I: Advent to Passion Sunday (Collegeville, Minnesota: The Liturgical Press, 1963), pp. 1659-1662.
Epistle and Gospel for December 8