Until recently, it was widely held that covenant theology was created in the middle of the seventeenth century by theologians such as Johannes Cocceius (1609–69). In fact, covenant theology is nothing more or less than the theology of the Bible. It is also the theology of the Reformed confessions. In the history of theology, the elements of what we know as covenant theology—the covenant of redemption before time between the persons of the Trinity, the covenant of works with Adam, and the covenant of grace after the fall—have existed since the early church.

Indeed, Reformed readers who turn to the early church fathers (c. AD 100–500) might be surprised to see how frequently they used language and thought patterns that we find very familiar. The covenant theology of the fathers stressed the unity of the covenant of grace, the superiority of the new covenant over the old (Mosaic) covenant, and that, because Jesus is the true seed of Abraham, all Christians, whether Jewish or gentile, are Abraham’s children. They also stressed the moral obligations of membership in the covenant of grace.

The covenant theology of the medieval church (c. AD 500–1500) was related to that of the early fathers but distinct in certain ways. In response to the criticism that Christianity gave rise to immorality, many teachers in the early church tended to speak about the history of redemption as the story of two laws, the old (Moses) and the new (Christ). They often tended to speak of grace as the power to keep the law in order to be justified.

This habit only increased in the medieval church. The major theologians argued that God can call people righteous only if they are actually inherently righteous. This, they thought, will happen when sinners are infused with grace and cooperate with that grace, so that they become saints. In this scheme, sanctification is justification, faith is obedience, and doubt is of the essence of faith.

In medieval covenant theology, the word “covenant” became synonymous with “law.” They did not speak of a covenant of works and a covenant of grace. Rather, the grace of the covenant enables one to keep the law.

Late in the medieval period, some theologians began to stress the idea that God has given a kind of grace to all humans and made a covenant so that “to those who do what is in them, God does not deny grace.” In effect, God helps those who help themselves. The Reformation would not only reform the covenant theology of the early fathers but would wage full-scale war on the covenant theology of the medieval church.

When he rejected the medieval doctrine of salvation by cooperation with grace, Martin Luther (1483–1546) rejected the old law/new law understanding of redemptive history. He came to understand that all of Scripture has two ways of speaking: law and gospel. The law demands perfect obedience, and the gospel announces Christ’s perfect obedience to that law for His people as well as His death and resurrection for them.

Soon after Luther came to his Protestant views, others were reforming covenant theology along Protestant lines. In the early 1520s, Johannes Oecolampadius (1482–1531) was teaching what would later become known as the covenant of redemption between the Father and the Son from all eternity. He also distinguished between the covenant of works as a legal covenant and the covenant of grace as a gracious covenant. A few years later, Heinrich Bullinger (1504–75) published the first Protestant book devoted to explaining the covenant of grace. Like the early fathers, this work stressed the graciousness and unity of the covenant of grace.