Chapter 19 — Part II: The Sacraments — Penance
Section 74. Furthermore, these are conditions to which man is bound to yield obedience; for the law to which man is subject, be it natural, divine, or human, he is bound to obey. If, therefore, by force or fraud, the penitent has taken anything from his neighbour, he is bound to restitution. Likewise if, by word or deed he has injured his neighbour's honour or reputation, he is under an obligation of repairing the injury by procuring him some advantage or rendering him some service. Well known to all is the maxim of St. Augustine: The sin is not forgiven unless what has been taken away is restored.