Feast Of The Immaculate Conception

In the Constitution Ineffabilis Deus of 8 December, 1854, Pius IX pronounced and defined that the Blessed Virgin Mary "in the first instance of her conception, by a singular privilege and grace granted by God, in view of the merits of Jesus Christ, the Savior of the human race, was preserved exempt from all stain of original sin."

Prayer of the Immaculate Conception

O God, who by the Immaculate Conception of the Blessed Virgin Mary, didst prepare a worthy dwelling place for thy Son, we beseech thee that, as by the foreseen death of this, thy Son, thou didst preserve her from all stain, so too thou wouldst permit us, purified through her intercession, to come unto thee. Through the same Lord Jesus Christ, thy Son, who livest and reignest with thee in the unity of the Holy Spirit, God, world without end.
Amen.