Chapter 18 — Part II: The Sacraments — The Holy Eucharist
Section 73. Pastors should also adduce another passage from which it can be clearly seen that the true body and blood of our Lord are contained in the Eucharist. The Apostle, after having recorded the consecration of bread and wine by our Lord, and also the administration of Communion to the Apostles, adds: But let a man prove himself, and so eat of that bread and drink of the chalice; for he that eateth and drinketh unworthily, eateth and drinketh judgment to himself, not discerning the body of the Lord. If, as heretics continually repeat, the Sacrament presents nothing to our veneration but a memorial and sign of the Passion of Christ, why was there need to exhort the faithful, in language so energetic, to prove themselves? By the terrible word judgment, the Apostle shows how enormous is the guilt of those who receive unworthily and do not distinguish from common food the body of the Lord concealed in the Eucharist. In the same Epistle St. Paul had already developed this doctrine more fully, when he said: The chalice of benediction which we bless, is it not the communion of the blood of Christ? and the bread which we break, is it not the participation of the body of the Lord ? Now these words signify the real substance of the body and blood of Christ the Lord.