Studies on Baptism
There are two basic kinds of religions in the world. One kind is the religion of the broad way (Mat. 7:13-14). Although it appears to be many different ways rather than one way, Jesus teaches that all non-Christian thought is unified in at least one sense: it is fundamentally opposed to the God of the Bible. Non-Christian religions like Judaism, Islam, Mormonism, and Jehovah's Witness borrow from the Bible to greater or lesser degrees and therefore share in some characteristics of Biblical religion. Non-Christian religions like those of African tribes, Indian Hinduism, or Chinese Buddhism show the true character of the broad way more clearly. These religions find salvation and power through means that are essentially magical. Shamans, medicine men, and priests have special knowledge and special powers that give them access to the secrets of the world. They mediate whatever salvation there may be. Ethical instruction, to the degree that it exists at all, is secondary to magical methods of manipulating the gods or the forces of the world.
The religion of the narrow way is fundamentally different. It is covenantal. The covenant is a personal legal bond. In Biblical religion God's relationship with man is ethical because it is grounded in the covenant. To understand the covenantal teaching of the Bible, we must consider three things: The structure of the covenant, the nature of a covenant relationship, the two basic covenants that structure the message of the Bible.
The Structure of the Covenant
The covenant is best understood by considering an outline of the covenant derived from the structure of the book of Deuteronomy, the fullest expression of the covenant form in the Bible:
1. Transcendence: The covenant begins with God as Creator and King of the world. God alone is absolute Lord. He gives us His covenant as an act of grace. We must believe in Him and worship Him as our Savior.
2. Hierarchy: The covenant deals with man's relationships with other men and Him in this world. He has appointed authorities in Church, State, and Family to represent Him on earth. We must submit to legitimate authority.
3. Ethics: The covenant is an ethical relationship that includes instruction in righteousness that God's people may be equipped to live for His kingdom. God gives us commandments that cover all of life.
4. Oath: The covenant is based upon a self-maledictory oath. We promise to love Him and do His will. He blesses and curses us on the basis of their obedience or disobedience to His commandments.
5. Succession: The covenant is multigenerational. God makes provision for the transference of blessings and authority from generation to generation. Leaders in Church, State, and Family are required to train leaders for the next generation.
The simple THEOS outline of the covenant gives us a broad picture of what covenant relationships involve. Every aspect of the covenant is ethical: 1) confessing God's Lordship and submitting our hearts to Him in love, 2) submitting to the earthly authorities that He has placed over us, 3) keeping His commandments because we delight to do His will, 4) promising to do His will that we may be blessed, and 5) training the next generation that they may love and serve Him also. 
The Nature of a Covenant
The covenant is personal. In every aspect of the covenant it is God Himself with whom we relate. But the covenant is also legal and none the less personal because it is legal. In fact, being legal makes it more personal. When a man takes a marriage vow, promising to cherish, provide for and protect the woman God has given to be his wife, the fact of the legal bond renders the relationship deeper and more intimate not less so. God's relationship to the Church is symbolized by the marriage relationship (cf. Eph. 5:22ff.). We are in covenant with Him on the basis of an oath.
Just as a young Christian woman pledges to submit to her husband (Eph. 5:22) with no thought of "slavery" or "legalism," we take an oath to submit to God because we love Him and desire to do His will. Like the marriage oath, our covenant oath to God is an expression of faith. The covenant oath reveals the heart of Christianity: we promise God that we will keep His commandments because we believe that He loves us and that His commandments are the essence of wisdom and righteousness. Christianity is a religion of faith and love that are expressed in righteous living. This, not in spite of, but because of the fact that it is a covenantal, legal religion.
The Covenantal Structure of the Bible
There are two fundamental covenants in the Bible. The first covenant was the covenant with Adam in the Garden of Eden. Adam was the representative head of the human race. His actions in the Garden affected the entire race: "by the offense of one, judgment came upon all men to condemnation" (Rom. 5:18a). When Adam sinned, God graciously postponed the ultimate curse of the old covenant and promised the coming of a new covenant (Gen. 3:15). Throughout the entire period of the old covenant (Adam to Christ), God granted covenants to men like Noah, Abraham, Moses, and David. These men were both replacements of Adam and types of the coming Messiah. The covenants granted to them were renewals of the Adamic covenant which included progressively clearer and greater promises of the new covenant.
The new covenant is given in Christ. He is the last Adam. Whereas Adam and every other man failed to keep God's covenant, Christ faithfully accomplished God's will. The new covenant replaces the old covenant not by way of establishing a fundamentally different kind of relationship with God, but by fulfilling the real purpose of the old covenant and bringing us into an ethically right relationship with God. The principles of the old covenant--1) God is Lord, 2) men are appointed as His representatives in history, 3) men are required to keep His commandments, 4) men are blessed and cursed in history and eternity on the basis of their relationship with Him, 5) God deals not just with individuals but with groups over time--do not change. To put it in different words: The relationship with man that God established in the creation is not nullified by redemption, but restored and fulfilled by redemption.
The new covenant in Christ does not diminish man's responsibility to know the true God, it increases it. We now know that God is Triune, that the Messiah promised by the prophets is none other than God Himself. We know the meaning of the law of Moses more deeply than Israel of old because we have the life and the teachings of the only man who ever could or did keep the law. We have a revelation of His grace and truth that far surpasses that of the old covenant without in any way contradicting it:
These two verses demonstrate the relationship between the covenants well. On the one hand the new far surpasses the old. On the other hand, the new and the old are not contradictory. The new is the fulfillment of the old. Since it is in perfect harmony with the teaching of the old covenant, the new replaces the old by glorifying it not by destroying it.
This is why Christ is called the last Adam (1 Cor. 15:45). Paul is speaking of the resurrection in 1 Corinthians 15, but the contrast between the two Adams and the two kinds of bodies that Paul expounds may be applied to the new and old covenants. The old covenant is like the physical body, created by God and good in itself, it is under condemnation because of sin. The resurrection body is a new deathless body. Even though it is very different from our present body, it also resembles it. Christ's disciples recognized their Lord, except when God miraculously withheld them from understanding who it was. The new body is totally different in some ways and very much the same in others. So also the new covenant is both similar to and different from the old.
How does this relate to baptism? The answer is that baptism, like the Lord's Supper, is a covenantal ceremony. As we saw in the previous study, baptism must be understood in terms of the broader doctrine of the covenant. This leads us to a consideration of covenantal ceremonies, our next study.