Council of Trent: Session XXIV, Reformation, Chapter VII

CHAPTER VII. The virtue of the Sacraments shall, before being administered to the people, be explained by Bishops and Parish Priests; during the solemnization of mass, the sacred oracles shall be explained.

In order that the faithful people may approach to the reception of the sacraments with greater reverence and devotion of mind, the holy Synod enjoins on all bishops, that, not only when they are themselves about to administer them to the people, they shall first explain, in a manner suited to the capacity of those who receive them, the efficacy and use of those sacraments, but shall endeavour that the same be done piously and prudently by every parish priest; and this even in the vernacular tongue, if need be, and it can be conveniently done; and in accordance with the form which will be prescribed for each of the sacraments, by the holy Synod, in a catechism which the bishops shall take care to have faithfully translated into the vulgar tongue, and to have expounded to the people by all parish priests; as also that, during the solemnization of mass, or the celebration of the divine offices, they explain, in the said vulgar tongue, on all festivals, or solemnities, the sacred oracles, and the maxims of salvation; and that, setting aside all unprofitable questions, they endeavour to impress them on the hearts of all, and to instruct them in the law of the Lord.

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