Baptism and the Lord's supper are covenantal ceremonies. But they are not the first covenantal ceremonies in the Bible. From the beginning God provided a form of covenantal ceremony that "dramatized" the meaning of the covenant. But what was the nature of that covenantal ceremony? What is the nature of covenantal ceremonies throughout the Bible? To answer these questions, we must consider God's covenant with Adam and Eve and the Edenic covenant ceremony.
After God created Adam, the first thing He did was to prepare the Garden of Eden as man's dwelling place (Gen. 2:7-8). Adam apparently watched as the Garden was designed and made ready for him to live in. When all was prepared, Adam was placed in the Garden and given his commission as prophet, priest, and king of the old covenant (Gen. 2:15-17). The commandment not to eat of the tree of the knowledge of good and evil was preceded by the grant of freedom to eat of any and all trees of the Garden. Since there was only one other tree in the center of the Garden and since that tree was named the "tree of life," the invitation to eat freely of any tree was also more specifically an invitation to eat of the tree of life.
Adam was called upon to chose life in obedience to God and His covenant or death in rebellion against God (Gen. 2:16-17). He was given a choice between the Lord's supper and the devil's supper. But how would the tree of the knowledge of good and evil convey knowledge? How would the tree of life convey life? To answer these questions is to get at the heart of the issue of covenantal ceremonies.
Roman Catholic View of Ceremonies
There are two false views of the relationship between covenantal ceremonies and the blessings associated with them. First, Roman Catholic theology regards ceremonies as actually communicating the grace of God through the consecrated physical elements. The water of baptism is "holy water" that has the power to convey life to the recipient. The bread and the wine have supernatural power to bring blessing to those who eat. 
Applying the Roman Catholic view of Baptism and the Lord's supper to the Garden, we would have to think of the tree of the knowledge of good and evil as having a sort of magical power to impart knowledge to the one who eats of it. There seems to be support for this view in Genesis 3:22 where God says: "Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever." God expelled man from the Garden because he would live forever if he ate of the fruit of the tree of life. Doesn't that seem to imply that the tree had some sort of inherent power to give life? And if that is correct about the tree of life, wouldn't that also be the correct approach to the tree of the knowledge of good and evil? And to baptism and the Lord's supper?
While protestants cannot agree with this view, they must also admit that there is something of a apparently Biblical logic in it. The covenant signs in the Garden do seem to carry some sort of power. God Himself says that Adam and Even did gain knowledge of good and evil by eating of the tree (Gen. 3:22). Again it is God Himself who says that they will live forever if they eat of the tree of life. What does all this mean?
The problem with the Roman Catholic view is that it suggests a universe in which supernatural power freely floats around to be appropriated by anyone who has the right formula. The Catholic view of the sacraments carries with it an almost-magical view of all of reality that contradicts the Biblical doctrine of creation and God's sovereignty. Roman Catholicism holds to its almost-magical ideas in an inconsistent fashion and attempts to obviate the inevitable clash between the pagan ideas and Christian ideas unequally wedded in its theology. But the result is a contradictory system of thinking.
Zwinglian View of Ceremonies
The other false view of covenantal ceremonies is the view of Zwingle. This view is held today by many protestants in many denominations. Most, if not all, baptists hold to this view. Simply stated, Zwingle's position is the ceremonial actions themselves convey nothing. The only thing that counts is the heart. Calvin is apparently describing Zwingle's view when he speaks of some who regard baptism "as nothing but a token and mark by which we confess our religion before men". 
Applying this view of new covenant ceremonies to the situation in the Garden of Eden suggests that Adam's eating of the fruit of the tree of the knowledge of good and evil was a profession of his rebellion against God. From a Zwinglian perspective the eating itself, and the "elements" of the Edenic supper are irrelevant. The only thing that counts is the heart.
There is no doubt some truth in this. After all, what if Adam had agreed with Satan that God was evil and was withholding good from him, but instead of eating the fruit said, "I will find my own way to rebel"? Would Adam have then been faultless? Doesn't Adam's sin begin the moment he believes Satan rather than God? Even if we don't want to say that one's heart is the only thing that counts, no one can deny that the heart does count.
The problem with the Zwinglian view is that it does not seem to attach any special significance to the actual eating. If that is legitimate, why did God establish this ordinance to begin with? Why attach so much significance--eternal life or death--to the eating of these trees when all that counts is the heart?
Covenantal View of Ceremonies
When we look at these two inadequate views together, we get a hint about the true direction. On the one hand while we cannot accept the idea of magical power in the fruit of the trees, there is some kind of "power" involved here. On the other hand, while we cannot accept that partaking in the covenant sign is a mere profession, the importance of the heart attitude of the participant is paramount.
The key to the correct interpretation here is provided by the idea of the covenant. The covenant is a personal legal bond. God's covenant with Adam is a personal relationship in which faith and love are primary. The legal aspect of that relationship confirms and strengthens the personal. Adam's eating from the tree of the knowledge of good and evil is a personal rejection of God's love and authority in the form of a legally significant act.
It is not the fruit of the tree that conveyed death. The fruit of that tree was not ontologically different from the fruit of any other tree. It had no special "death inducing" chemical substance in it. The power of the tree was in the covenant. God's word of promise, "In the day you eat therefrom, you shall surely die" was the power that brought death to Adam and Eve. Their eating was a judicial act that included certain covenantal consequences because of the word of God that instituted that covenantal arrangement.
Consider the analogy of taking human life. Murder is a certain sort of taking of human life. It is defined by law, not by the physical act itself. If I take the life of an enemy in war, I am praised. If I take the life of my next door neighbor, I am hanged, or in the modern world, I get a "life sentence" to prison for the next two to five years. It is the law that defines the act of murder. When one commits the act defined by law as murder, even though the actual physical deed may be the same as what one does in a time of war, the meaning of the deed is totally different.
The only act Adam performed was to eat. But that eating had a special legal definition, established by the covenant God granted to Adam. Since God is truth, He keeps His word. If after taking the fruit of the tree of the knowledge of good and evil, Adam had taken fruit from the tree of the life, he would have been forever confirmed in his rebellion against God, not because that tree had inherent power, but because God had established the legal significance of eating from that tree by His covenant with Adam.
Covenantal ceremonies are legally designated symbols that bring God's blessing or curse. They are, as the Catholics affirm, always effecacious, but they do not always "communicate grace." Rather, the ceremonies of the covenant are dramatic oath-making acts which God has established. If Adam had rejected Satan and eaten from the tree of life, he would have been confirming God's covenant. In that case he would have been blessed. Since he rejected God's covenant instead, his eating of the sacramental tree brought a curse.
These same basic covenantal principles are found throughout the ceremonies recorded in the Old Testament. Baptism and the Lord's supper too are oath-taking, covenantal ceremonies that operate like all other covenantal ceremonies in the Bible. To receive them rightly certainly brings God's blessing. To take them presumptuously no less certainly brings God's curse (cf. 1 Cor. 11:23ff.).
. Institutes of the Christian Religion, 4:15:1.