Council of Trent: Session XIV, On The Most Holy Sacrament Of Penance, Canon VII

ON THE MOST HOLY SACRAMENT OF PENANCE

CANON VII.--If any one saith, that, in the sacrament of Penance, it is not necessary, of divine right, for the remission of sins, to confess all and singular the mortal sins which after due and diligent previous meditation are remembered, even those (mortal sins) which are secret, and those which are opposed to the two last commandments of the Decalogtie, as also the circumstances which change the species of a sin; but (saith) that such confession is only useful to instruct and console the penitent, and that it was of old only observed in order to impose a canonical satisfaction; or saith that they, who strive to confess all their sins, wish to leave nothing to the divine mercy to pardon ; or, finally, that it is not lawful to confess venial sins ; let him be anathema.

Translation: J. Waterworth, The Canons and Decrees of the Council of Trent (1848), Hanover Historical Texts Project transcription (1995).