Saint Pius X wrote the following encyclical Ad Diem Illum Laetissimum on the feast of Our Lady’s Purification, February 2, 1904:
An interval of a few months will again bring round that most happy day on which, fifty years ago, Our Predecessor Pius IX., Pontiff of holy memory, surrounded by a noble crown of Cardinals and Bishops, pronounced and promulgated with the authority of the infallible magisterium as a truth revealed by God that the Most Blessed Virgin Mary in the first instant of her conception was free from all stain of original sin. Read the full text here.
