6 Can there be, Venerable Brethren, a greater or more urgent duty than to preach the unsearchable riches of Christ ( Ephesians iii. 8) to the men of our time? Can there be anything nobler than to unfurl the "Ensign of the King" before those who have followed and still follow a false standard, and to win back to the victorious banner of the Cross those who have abandoned it? What heart is not inflamed, is not swept forward to help at the sight of so many brothers and sisters who, misled by error, passion, temptation and prejudice, have strayed away from faith in the true God and have lost contact with the joyful and life-giving message of Christ?
Source: Summi Pontificatus (Vatican.va)