St. Thomas Aquinas teaches that the Eucharist has a threefold significance regarding the past, present, and future. The Eucharist involves the past, because it is the re-presentation of Christ’s sacrifice on Calvary. It is not a performance of what happened, or a re-telling of a story, and it isn’t a ritual for the sake of a ritual. When we celebrate the Holy Sacrifice of the Mass, we are taken outside of space and time to Calvary, where we see, with the eyes of faith, Christ’s sacrifice on the Cross.
The present reality is the ecclesiastical unity of the Body of Christ. We gather as a faith community, to worship almighty God, and receive the Bread of Life in communion together. This is why we call it Holy Communion and also the reason why only initiated Catholics can receive the Eucharist. By coming up as a corporate body to receive the risen Jesus in the Eucharist, we are stating that we believe in the Eucharist and in the teachings of our One, Holy, Catholic, and Apostolic faith. Lutherans, Muslims, Jews, non-denominational Christians, etc. do not profess or believe in what our community does, so they do not receive Holy Communion.
“With regard to the future,” St. Thomas writes, “it has a third meaning, inasmuch as this Sacrament [the Eucharist] foreshadows the Divine fruition which shall come to pass in heaven; and according to this it is called Viaticum, because it supplies the way of winning thither.” (Summa, III, 73, 4, c.). When we attend the Holy Sacrifice of the Mass, we are getting a foretaste of heaven. We read in the Book of Revelation what heaven will look like: everyone dressed in white, worshiping the Lamb of God on His throne, singing hymns of praise. This is exactly what we do at Holy Mass. The Eucharist shows us and prepares us for the reward we all hope to receive when our earthly pilgrimage comes to an end.
Speaking of our earthly pilgrimage, St. Thomas also says the following: “…in our pilgrimage, [Christ] does not deprive us of His bodily presence, but unites us with Himself in this Sacrament through the truth of His Body and Blood, always seen in their sacrificial condition…Hence, this Sacrament is the sign of supreme charity, and the uplifter of our hope, from such familiar union of Christ with us.” (Summa, III, 75, 1, c.).
In understanding the Eucharist involving the past (bringing us back to the Sacrifice of Christ on Calvary), present (our unity as the Body of Christ), and future (giving us a foretaste of Heaven), we see the importance of celebrating and receiving the Eucharist in person. Praying and celebrating Holy Mass from a distance at home is still a valid way to participate in the sacred mysteries when our health demands us to stay home; but, it’s obviously not the ideal. This is why Sunday Mass is obligatory for disciples of Jesus, so we can participate in the Sacrifice of Christ, receive His Body and Blood in Holy Communion, and look forward with great hope to our eternal reward.