19 If then God has such a horror of sin as to have willed to keep free the future Mother of His Son not only from stains which are voluntarily contracted but, by a special favor and in prevision of the merits of Jesus Christ, from that other stain of which the sad sign is transmitted to all us sons of Adam by a sort of hapless heritage: who can doubt that it is a duty for everyone who seeks by his homage to gain the heart of Mary to correct his vicious and depraved habits and to subdue the passions which incite him to evil?
Source: Ad Diem Illum Laetissimum (Vatican.va)