Chapter 19 — Part II: The Sacraments — Penance
Section 26. Moreover -- and this is the principal reason -- since what is exteriorly done, both by priest and penitent, signifies the inward effects that take place in the soul, who will venture to deny that Penance is invested with the nature of a proper and true Sacrament ? For a Sacrament is a sign of a sacred thing. Now the sinner who repents plainly expresses by his words and actions that he has turned his heart from sin; while from the words and actions of the priest we easily recognise the mercy of God exercised in the remission of sins.