Tomorrow we celebrate the Solemnity of the Immaculate Conception of the Blessed Virgin Mary, which references Mary's conception in her mother's womb without the stain of Original Sin:
An essential part of God's plan for the mother of his Son was that she be conceived free from Original Sin. "Through the centuries the Church became ever more aware that Mary, "full of grace" through God, was redeemed from the moment of her conception" (CCC, no. 491). In anticipation that she was to bear the Son of God, Mary was preserved from the time of her conception from Original Sin. We call this the Immaculate Conception. No sin would touch her, so that she would be a fitting and worthy vessel of the Son of God.
The Immaculate Conception does not refer to the virginal conception and birth of Christ, but rather to Mary's being conceived without inheriting Original Sin. In the course of time, the doctrine of the Immaculate Conception became more precisely enunciated, as its truth-long supported by the universal popular devotion of the faithful-was better understood by deepening theological inquiry. In 1854, Pope Pius IX proclaimed this dogma infallibly: that is, in his role as supreme teacher of the Church, he declared that this doctrine is divinely revealed and must be accepted with faith by the entire Church. (United States Catholic Catechism for Adults, 142-143)
The bishops commended the United States to the patronage of Mary under the title of the Immaculate Conception in 1846. (Hence the name of the National Shrine of the Immaculate Conception in Washington, D.C.) December 8th became a nationwide holy day in 1885. (Essential Guide to Seasons and Saints, 120)
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