Chapter 18 — Part II: The Sacraments — The Holy Eucharist
Section 24. The Eucharist Signifies Three Things — It must, therefore, be diligently explained what the Sacrament of the Eucharist signifies, that the faithful, beholding the sacred mysteries with their eyes, may also at the same time feed their souls with the contemplation of divine things. Three things, then, are signified by this Sacrament. The first is the Passion of Christ our Lord, a thing past; for He Himself said: Do this for a commemoration of me, and the Apostle says: As often as you shall eat this bread, and drink the chalice, you shall show the death of the Lord, until he come.