23 And if, as the Apostle declares, faith is nothing else than the substance of things to be hoped for" ( Hebr . xi. 1) everyone will easily allow that our faith is confirmed and our hope aroused and strengthened by the Immaculate Conception of the Virgin. The Virgin was kept the more free from all stain of original sin because she was to be the Mother of Christ; and she was the Mother of Christ that the hope of everlasting happiness might be born again in our souls.
Source: Ad Diem Illum Laetissimum (Vatican.va)