As to the question whether upon that day it is right to partake of food before either offering or partaking of the Eucharist, these words in the Gospel might go far to decide our minds, “As they were eating, Jesus took bread and blessed it;” taken in connection with the words in the preceding context, “When the even was come, He sat down with the twelve: and as they did eat, He said, Verily I say unto you, that one of you shall betray Me.” For it was after that that He instituted the sacrament; and it is clear that when the disciples first received the body and blood of the Lord, they had not been fasting.
Must we therefore censure the universal Church because the sacrament is everywhere partaken of by persons fasting? Nay, verily, for from that time it pleased the Holy Spirit to appoint, for the honour of so great a sacrament, that the body of the Lord should take the precedence of all other food entering the mouth of a Christian; and it is for this reason that the custom referred to is universally observed. For the fact that the Lord instituted the sacrament after other food had been partaken of, does not prove that brethren should come together to partake of that sacrament after having dined or supped, or imitate those whom the apostle reproved and corrected for not distinguishing between the Lord’s Supper and an ordinary meal. The Saviour, indeed, in order to commend the depth of that mystery more affectingly to His disciples, was pleased to impress it on their hearts and memories by making its institution His last act before going from them to His Passion. And therefore He did not prescribe the order in which it was to be observed, reserving this to be done by the apostles, through whom He intended to arrange all things pertaining to the Churches. Had He appointed that the sacrament should be always partaken of after other food, I believe that no one would have departed from that practice. But when the apostle, speaking of this sacrament, says, “Wherefore, my brethren, when ye come together to eat, tarry one for another: and if any man hunger, let him eat at home; that ye come not together unto condemnation,” he immediately adds, “and the rest will I set in order when I come.” Whence we are given to understand that, since it was too much for him to prescribe completely in an epistle the method observed by the universal Church throughout the world, it was one of the things set in order by him in person, for we find its observance uniform amid all the variety of other customs. (Letter to Januarius)