16 The Virgin Mary herself desired this tie. "What the Sovereign Pontiff defined in Rome through his infallible Magisterium, the Immaculate Virgin Mother of God, blessed among all women, wanted to confirm by her own words, it seems, when shortly afterward she manifested herself by a famous apparition at the grotto of Massabielle. . ." Certainly the infallible word of the Roman Pontiff, the authoritative interpreter of revealed truth, needed no heavenly confirmation that it might be accepted by the faithful. But with what emotion and gratitude did the Christian people and their pastors receive from the lips of Bernadette this answer which came from heaven: "I am the Immaculate Conception!"
Source: Le Pelerinage de Lourdes (Vatican.va)