19 There is still another and not lesser advantage which the Church earnestly seeks for her children from the Rosary, and that is the faithful regulation of their lives and their conduct in keeping with the rules and precepts of their holy religion. For if, as we all know from Holy Scripture, "faith without works is dead"(4)because faith draws its life from charity and charity flowers forth in a profusion of holy actions-then the Christian will gain nothing for eternal life from his faith unless his life be ordered in accordance with what faith prescribes. "What shall it profit, my brethren, if a man say he bath faith, but hath not works? Shall faith be able to save him?"(5) A man of this sort will incur a much heavier rebuke from Christ the Judge than those who are, unfortunately, ignorant of Christian faith and its teaching: they, unlike the former, who believes one thing and practices another, have some excuse or at least are less blameworthy, because they lack the light of the Gospel.
Source: Magnae Dei Matris (Vatican.va)