Article — Vermeersch, Theologia Moralis
To n. 393. - Appendix X. Historical Matters Concerning Fasting Before Holy Communion
The general law of preserving the natural fast before Communion already existed, without doubt, in the fourth century. St. Augustine (epist. ad Ianuarium, n. 8, P. L. 33, 203) bears witness to it for us in these words: "For on this account it pleased the Holy Spirit that, in honor of so great a sacrament, the Lord's Body should enter the mouth of a Christian before other foods; for therefore this custom is observed throughout the whole world." And the observance is inculcated by the so-called Apostolic Constitutions and by monuments which refer to them or are connected with them. Among these stand out the Egyptian Church Constitutions (which, as is probable, are the Αποστολική παράδοσις of St. Hippolytus of Rome, toward the beginning of the third century).
Thursday in the Lord's Supper was excepted; the reason for this exception, by no means mystical, is indicated to us thus by St. Augustine. "For I do not think this was instituted except because many, and almost all in most places, were accustomed to bathe on that day... And because some fast, it is offered in the morning on account of those dining, because they cannot bear fasts and baths together; but toward evening on account of those fasting." The holy Doctor derives the very usage of bathing from the custom of those to be baptized, who then, after laying aside the filth contracted by the Lenten observance, disposed themselves for Baptism by purification of the body (op. cit., n. 9, 10).
Where we treated of fasting before Mass, we alleged the canons of the Council of Laodicea and of the Third Council of Carthage, which urged the obligation of fasting even on the Lord's Supper. Already before the fourth century Tertullian, besides the celebrations before dawn, mentions the bread which (at home) "we are accustomed to taste before every other food" (Ad uxorem, l. II, c. 5, P. L. 2, 1296). Yet in the first times, as is manifest from 1 Cor. 11, 20, the taking of food preceded the eucharistic banquet.