The word “covenant” (בְּרִית) is used for the first time in the Hebrew Bible referring to the salvation of the world. The Biblical concept of “covenant” is to be understood as God’s redemptive instrument for Israel and the nations. From the Adamic to the Davidic covenant, God establishes an organic development in the process of redemption for all the nations through Israel. Israel's calling as the servant of God is to bring blessing to the nations and to reclaim them for God. Despite the fall in the garden of Eden and the curse that followed, God’s purpose for humanity did not change. As intended with Adam and Eve, God desires that the humanity will dwell with Him. At the same time, as the Westminster Shorter Catechism puts it: “man's chief end is to glorify God and enjoy him forever.”
1. The Adamic Covenant and its priestly function
The covenant of works that God established with Adam in the garden of Eden, although not explicitly named as such in Scriptures, is essentially referred to as the covenant of commencement, or the “covenant of life” (The Westminster Shorter Catechism 12) “because to obey its stipulations would have given life”. The Adamic covenant identifies the elements that can be found in the covenants to follow, namely: the parties involved (God and Adam), the covenant conditions (Genesis 2:16-17), blessings and curses (Genesis 1:28, 2:17), the principle of representation (Adam representing the human race), and finally the sign of the covenant. Most scholars agree that the tree of life is a sign of the Adamic covenant, though it remains debatable for some.
The priestly function can be found for the first time in Adam, the first representative of mankind. He is the first priest in the garden of Eden whose role was to fulfil the covenant of works. Through his mediation his descendants would either continue to receive the blessings of God’s presence or the curse of sin that leads to isolation from God. The mediation between God and man that failed in Adam by his disobedience succeeded in Christ by His perfect obedience (Hebrews 9:15; 1 Corinthians 15:21-23; 44-49). In Romans 5:12-21 apostle Paul offers a comparison of the persons and actions of Adam and Jesus Christ. Adam's one sin resulted in condemnation and death for his ordinary descendants. Jesus's obedience and death resulted in justification and life for his people.
2. The Noahic Covenant: the preservation and the beginning of redemption
The Noahic covenant is also called the covenant of preservation. It emphasises the close interrelation of the creation, preservation, and redemption. A distinctive of God’s covenant with Noah relates to His redemptive grace towards Noah and his family. One cannot think of Noah without being reminded of God’s universal judgment on the human race by means of the flood. The judgment of the flood that preceded the covenant is considered as a de-creation and its abatement as an act of re-creation. In Genesis 9:9-13 God confirms His providential preservation of nature and life which is the essence of this covenant. A distinction between the Noahic covenant and the Adamic covenant lies in the fact that in contrast with Adam’s disobedience therefore violating the covenant conditions, Noah (representing the human race), obeyed God and found favour in the eyes of the Lord (Genesis 6:8-9). As a sign of the Noahic covenant, God sets His “bow in the cloud” (Genesis 9:13) to serve as a reminder that “never again shall the water become a flood to destroy all flesh” (Genesis 9:15).
The preservation of mankind following the deluge confers salvation to Noah and his family which points to Christ’s redemptive plan through the new covenant. God’s covenant with Noah required the faith and obedience of Noah in the building of the ark in order to obtain the salvation offered. In the same way in the new covenant God’s salvation is offered by grace alone through faith that produces obedience (Ephesians 2:8-9; 2 Timothy 1:9). It may be that God's grace had kept Noah from sinking to the levels of depravity found among his contemporaries, but nothing indicates that Noah's favoured position arose from anything other than the grace of the Lord himself.
3. The Abrahamic Covenant: the promise of blessings for all the nations
The Abrahamic covenant or otherwise called the covenant of promise is in essence God’s series of promises made to Abraham. The relationship between God and Abram involved the creation of a new family marked by the divine call to go out of his father’s house as mentioned in Genesis 12:1. Genesis 15 and 17 together list God’s promises to Abraham, first concerning his descendants (his immediate family and the multitude of nations that Abraham would father), and secondly the promised land of Canaan. Through the Abrahamic covenant not only Abraham and Israel would benefit from the promised blessings but all the families of the earth (Genesis 12:3). Additionally, a physical sign was attached to this covenant. The sign of this covenant (circumcision) physically marks the distinction of God’s people from the gentiles. God’s covenant with Abraham becomes the theological foundation of His promises to Israel, anticipating the blessings they will enjoy in terms of population, country, and global influence. The nations are the target of God's redemptive acts in history, and Israel was brought forth as God's means to that redemption. God had called out Abram and created Israel to undo the curse and to bring blessings to all the families of the earth. Circumcision as a sacrament represents the inherent condition for the covenant ratification. Moreover, as the seal of this covenant it is so closely related to the covenant that the covenant itself is identified as ‘the covenant of circumcision’.
God’s covenantal promise to Abraham that “all the nations of the earth shall be blessed” (Genesis 22:18) in his offspring is a twofold promise with far reaching implications. Firstly, it is miraculously fulfilled in the nation of Israel through Abraham’s descendants: Isaac and Jacob. God’s intent for the newly established nation was its consecration and setting apart for its mission: to be “a kingdom of priests and a holy nation” (Exodus 19:6). “Israel was to be a living catechism for the nations—that was their public, international calling”.This, however, came with a condition that they obey God’s voice and keep His covenant (Exodus 19:5). Secondly, it is fulfilled through the Gentile multitude “who share the faith of Abraham” (Romans 4:16). Despite Israel’s failure to fulfil its priestly mission, the promise of blessings for all the nations is however, fulfilled in Christ, the great high priest (Hebrews 14:4) and thus they put their faith in Christ. Apostle Paul identifies the Gentiles who by faith in Jesus are justified (Galatians 3:8), and therefore, are the sons of Abraham (Galatians 3:7), heirs according to the promise (Galatians 3:29).
4. The Mosaic Covenant: the law
The Mosaic covenant is referred to as the covenant of law. The only way to re-gain the intimacy between God and humanity that was lost in the garden of Eden is through humans obeying God’s perfect rules of righteousness. These rules or laws are the essence of the Mosaic covenant. The giving of the law on Mount Sinai achieves at least two objectives. Firstly, the law provides a way to re-enter into God’s presence for the first time since the fall. Note that “virtually every law and commandment listed from Exodus 25 until the consecration of the tabernacle in Leviticus 10 pertain directly to the sanctuary”. Secondly, the moral, civil, and ceremonial laws give knowledge of God. God’s deliverance of the Israelites from the land of Egypt would lead to a knowledge of His name and power among not only His chosen people but also the Egyptians and beyond as stated in Exodus 7:5. Such knowledge is linked inseparably to His dwelling among His people. Starting with Israel being brought out of Egypt to Mount Sinai and further into His presence “through the tabernacle cultus”, God has one purpose for His people and that is to worship Him and to be in His presence. The sign of the Mosaic covenant is the Passover meal. It is precisely prescribed for Israel and future generations as a memorial sacrament so they shall never forget how God brought their ancestors out of Egypt, the land slavery. Crucially, this covenant of law is conditioned by the covenant of promise. That is, only those who are circumcised are eligible for participation in the Passover meal.
The Mosaic law is one of the most distinct characteristics of the Mosaic covenant and of the Old Testament altogether. Not accidentally the failure to obey the law, firstly by Adam in the garden of Eden and later by the whole nation of Israel, is at the core of the need for the gospel. Both Adam and Israel failed to obey and consequently to fulfil their priestly mission. Therefore, a new priest was needed to fulfil the law and to mediate between God and man (1 Timothy 2:5), namely Christ Jesus. In Mathew 5:17-20 we are told that Jesus came to fulfil the law by His perfect obedience. The direct connection between the law and Christ is explained by the apostle Paul who concludes that the law of Moses is but a mere guardian until Christ came, in order that He may bring justification by faith (Galatians 3:24). Christ does not only fulfils the law by His obedience but also fulfils the roles of the high priest and perfect atonement through His sacrifice. He is indeed “the end of the law for righteousness to everyone who believes” (Romans 10:4).
5. The Davidic Covenant: the kingship
The Davidic covenant is a covenant of the Kingdom which establishes how God shall rule and dwell among His people. “The essence of the covenant is manifested in God’s relation to David”. God promises David that there are two kingdoms to be made permanent and they shall be linked together. First, the Lord sovereignly establishes David's dynasty. Secondly, the dynasty of David shall establish the Lord's eternal throne. The sign of this covenant is God’s eternal throne as revealed in 2 Samuel 7:13-16. Two features are central to the Davidic covenant: Israel’s kingship and the location of Jerusalem. The Ark of the Covenant is a physical symbol of God’s Throne. Therefore, by bringing the Ark into Jerusalem David “inaugurated the concept of theocracy” there: God’s ruling through David and His Throne in Jerusalem. However, “the kingdom of God must be placed in the category of an ‘anticipative’ realisation in proper keeping with the entire scope of Old Testament experience”. The shadow-kingdom of Israel had God reigning in their midst, but it was nonetheless only a shadow of the reality to come. The principle of God’s deliverance and the peoples’ belonging to Him is fulfilled when God dwells among his people through the temple of Solomon (1 Kings 8:54-61). An interesting detail in the covenantal development can be found in 1 Samuel 7:25-29 where David asks God to confirm the promises made concerning his dynasty. On four occasions David uses “Adonai Yahweh” (“Lord God”) when referring to God. This does not appear anywhere else in Samuel or in the parallel passage in Chronicles. It does appear, however, in Genesis 15:2, 8 where Abraham speaks to God about the promise of the seed. The high point of Israel’s history and the immediate fulfilment of the Davidic covenant is manifested in the early reign of Solomon. However, this does not last because of Israel’s disobedience. If the law given to Moses pointed to the ultimate High Priest who was to come, David’s throne and the kingship line established was to point to the King who was to come, both being fulfilled in Jesus Christ.
God’s promise of an eternal throne begins with David’s kingship which is only a foreshadow of Christ’s reign. The concept of kingship, however, does not appear for the first time at the institution of Saul’s or David’s kingship. It goes back to Genesis 1-2 where every human being was to rule over creation for the glory of God. God's rule on earth is accomplished through the agency of human dominion. However, sinful humans are not able to conquer the serpent except for Jesus who knew no sin (2 Corinthians 5:21). Jesus’ coming as king is announced in Genesis 3:15 as the seed of the woman who shall bruise the serpent’s head, an illustration pointing to Christ’s victory on the cross. God’s promise that He will establish David’s throne and kingdom forever (2 Samuel 7:13) is echoed in Isaiah’s prophecy saying that the LORD will “reign on Mount Zion and in Jerusalem” (Isaiah 24:23). This was difficult to believe for the Israelites particularly coming in a time of decline for the nation. Nevertheless, God assures His people that He will remember His covenant and will establish an everlasting covenant with them (Ezekiel 16:60).
Throughout the covenants discussed above one can find the elements identified by stipulations, promises, signs and reminders that God sovereignly put together for the purpose of His redemptive plan. The work of God’s grace through each covenant is best summarised in the Westminster Confession of Faith which says: “although reasonable creatures do owe obedience unto him as their Creator, yet they could never have any fruition of him as their blessedness and reward, but by some voluntary condescension on God's part, which he hath been pleased to express by way of covenant” (WCF, chapter 7.1). The thematic unity of the covenants rests on God’s relationship to His people. “I shall be your God, and you shall be my people” is one phrase that repeats itself again and again pointing out to God’s desire and purpose for creation—that His people will dwell in His presence. “Ultimately, a restoration of the nations to God will require an exodus, for the exodus pattern is nothing less than the reversal of exile, nothing less than resurrection from the dead”. And with the coming of the Messiah, “the new covenant has been inaugurated, redemption has been procured, and restoration has begun—first, spiritually, and in the last day, materially”.
 Robertson, O., 1985. The Christ of the covenants. Phillipsburg, N.J: Presbyterian and Reformed Pub. Co, p.93.  Waters, G., Reid, J. and Muether, J., 2020. Covenant theology. Crossway Books, p.590.  Ibid, 66  Beale, G., 2005. The temple and the church's mission. Leicester: Apollos, pp.66-67.  Waters, G., Reid, J. and Muether, J., 2020. Covenant theology. Crossway Books, p.80.  Robertson, O., 1985. The Christ of the covenants. Phillipsburg, N.J: Presbyterian and Reformed Pub. Co, p.110.  Ibid. 111, 113  Ibid. 123  Ibid. 110  Waters, G., Reid, J. and Muether, J., 2020. Covenant theology. Crossway Books, p.136.  Robertson, O., 1985. The Christ of the covenants. Phillipsburg, N.J: Presbyterian and Reformed Pub. Co, p.148.  Morales, L., 2020. Exodus Old and New. IVP Academic, p.16.  Ibid. 95  Ibid. 77-78  Ibid. 78  Ibid. 75  Robertson, O., 1985. The Christ of the covenants. Phillipsburg, N.J: Presbyterian and Reformed Pub. Co, p.229.  Ibid. 231  Ibid. 232-233  Ibid. 251  Ibid. 241  Ibid.  Waters, G., Reid, J. and Muether, J., 2020. Covenant theology. Crossway Books, p.181.  Morales, L., 2020. Exodus Old and New. IVP Academic, p.16.  Waters, G., Reid, J. and Muether, J., 2020. Covenant theology. Crossway Books, p.209.