The first beatitude cited in the Gospel is that of faith, and it refers to Mary: “Blessed is she who believed” (Lk 1:45). These words, spoken by Elizabeth, highlight the contrast between Zechariah’s disbelief and Mary’s faith. On receiving the message about the future birth of his son, Zechariah had found it hard to believe, judging it impossible since both he and his wife were advanced in age.
At the Annunciation Mary is confronted with an even more surprising message, the proposal that she become the mother of the Messiah. She does not react with doubt to this prospect, but limits herself to asking how the virginity to which she feels called could be reconciled with the vocation to motherhood. To the reply of the angel, who points out the divine omnipotence working through the Spirit, Mary gives her humble and generous consent.
At that unique moment in human history, faith plays a decisive role. St Augustine rightly states: “Christ is believed and conceived through faith. First, the coming of faith takes place in the Virgin's heart, followed by fruitfulness in the mother’s womb” (Sermo 293, PL 38, 1327).
John Paul II
Excerpt from John Paul II, General Audience, 6 May 1998