Because of our historical controversy with the Roman Catholic Church, and the subsequent Zwinglian over-reaction (adopted by most evangelical communities), the Lord’s table has become a naturalistic liturgical afterthought. In services I've attended, participated in and even led, there's always been a concerted effort to explain that nothing mystical is actually taking place, and that the entire ceremony is nothing more than an occassion for self-examination. But for Paul (and both Lutheran and Calvinistic traditions), communion wasn’t just an “ordinance” in the sense of a regulation which the church is supposed to meet in order to be “up to code”; he considered the holy meal “spiritual food” and “spiritual drink”. For all of the Reformers' sola fide conviction, for the most part they didn't seem to share the soteriological queasiness with which we repeat the words "this is my body" and "this is my blood". They affirmed with equal vigor that bread and wine can’t save anybody. They ardently protested against the idea that priests could somehow transform these elements into the actual flesh and blood of Christ by cultic incantation.
Yet, with Paul, they say communion as an act of mystical, spiritual fellowship both with Jesus and with one another. In verses 15-16 Paul declared that the cup is a means of blessing in which we share in Christ’s body and his blood. The children of Israel in the wilderness were supernaturally sustained by God not just physically, but spiritually; by the manna from heaven and the water from the rock which Moses struck. In their eating and drinking they tangibly experienced God’s deep personal commitment to delivering them from their slavery and bringing them into the new land; they were vividly reminded of their total dependence upon Him for their every provision. In eating, they entered into fellowship with God; they sat at His table. But they also entered into fellowship with one another. This dependence and salvation wasn’t just experienced by one, two or a two-hundred of them but by every single Israelite in the desert. They were delivered as a community, as a fellowship as a family. They all ate the same spiritual food and they all drank the same spiritual drink.
But notice that there was nothing automatically sanctifying about eating this meal; it didn’t automatically reconcile them to God, and it didn’t magically reconcile them to one another. In fact, Paul reminds us that even after receiving spiritual food and spiritual drink they still “craved evil things”. They weren’t satisfied by the meal God was providing; and so verse 6 says that their hunger turned to lust, and in verse 7 their lust turned to immorality, and verse 10 says that these evil cravings and all their attempts to fill it brought not contentment, not satisfaction, not full bellies, but grumbling. God was displeased with them, and he poured out His wrath upon them; but even before this there was judgment, because as they sought to satisfy their hunger with idolatry and immorality, they remained hungry, and they died in their discontentment.
The point here is that Christ is our spiritual food and spiritual drink, not just for when we were converted, not just for yesterday, but for the present, and for every moment we call “now”. He’s given to us in order to satisfy our cravings; and so this meal which we share isn’t just a law to observe; Paul says its one means by which we share in the body and blood of Christ and find continual food to sustain our spiritual lives. It’s a reminder that we must both receive Christ and flee from idols not once (at conversion), but always and “as often as you eat of it” and “as often as you drink it”. And he doesn’t say that we need to do that not by simply speaking about it. We receive these graces and proclaim His death until He comes by actually eating of the bread and drinking from the cup.
Consider this lengthy quote from Calvin as to the importance of the bread and the cup for our spiritual sustenance:
“For as God, regenerating us in baptism, ingrafts us into the fellowship of his Church, and makes us his by adoption, so we have said that he performs the office of a provident parent, in continually supplying the food by which he may sustain and preserve us in the life to which he has begotten us by his word. Moreover, Christ is the only food of our soul, and, therefore, our heavenly Father invites us to him, that, refreshed by communion with him, we may ever and anon gather new vigour until we reach the heavenly immortality. But as this mystery of the secret union of Christ with believers is incomprehensible by nature, he exhibits its figure and image in visible signs adapted to our capacity, nay, by giving, as it were, earnests and badges, he makes it as certain to us as if it were seen by the eye; the familiarity of the similitude giving it access to minds however dull, and showing that souls are fed by Christ just as the corporeal life is sustained by bread and wine. We now, therefore, understand the end which this mystical benediction has in view—viz. to assure us that the body of Christ was once sacrificed for us, so that we may now eat it, and, eating, feel within ourselves the efficacy of that one sacrifice,—that his blood was once shed for us so as to be our perpetual drink. This is the force of the promise which is added, “Take, eat; this is my body, which is broken for you” (Mt. 26:26, &c.). The body which was once offered for our salvation we are enjoined to take and eat, that, while we see ourselves made partakers of it, we may safely conclude that the virtue of that death will be efficacious in us. Hence he terms the cup the covenant in his blood. For the covenant which he once sanctioned by his blood he in a manner renews, or rather continues, in so far as regards the confirmation of our faith, as often as he stretches forth his sacred blood as drink to us" (Jean Calvin and Henry Beveridge, Institutes of the Christian Religion, IV, xvii, 1; emphasis mine)."The Lord's table is more than just a commemorative ceremony; it's a means of grace by which we are drawn into intimate fellowship with God.