21 And finally, Pius IX exhorted all the faithful to prepare themselves worthily and joyously for the First Vatican Council by ridding their souls of every stain of sin and the punishment due to sin. "It is certain," he said, "that men's prayers are more pleasing to God if they go up to Him from a pure heart; from souls, that is, that are free from all sin."(21)
Source: Paenitentiam Agere (Vatican.va)