From Adam to Abraham
Man had scarcely fallen into sin before God approached him with his overtures of grace. He promised Adam and Eve that he would send a mighty deliverer and redeemer. In Genesis 3:15 we have God's first revelation of the covenant of grace to man. God definitely promised man that there would be a conflict between Satan and the seed of the woman and that the seed of the woman would be victorious. "It [a descendant of Eve] shall bruise thy [Satan's] head, and thou [Satan] shalt bruise his [Christ's] heel." God manifested his grace here in two ways. First, he would make Adam and Eve enemies of Satan and therefore friends of God. Second, through the promised Redeemer God would break the power of Satan over men. When Christ died on Calvary's cross, Satan's power was broken. Wherever the gospel of the crucified One is preached with the blessing of the Spirit, Satan is powerless to enslave.
This covenant of grace to Adam gives us but a bare outline of God's plan of redemption. There is not revealed in this covenant all that we might like to know. It is rather general and indefinite. We might wish we knew just what kind of redeemer Adam and Eve expected. We might wish that we were told clearly the precise conditions that Adam and Eve had to fulfill before God regarded them as his friends once more. These details are not revealed. But of one thing we may be certain; God reveals elsewhere in his Word that "no man cometh unto the Father but by me [Christ]"; therefore, Adam and Eve must have trusted in the promised Deliverer for salvation, for otherwise they never could have become friends of God, reconciled to him.
From Abraham to Moses
The covenant of grace in the Old Testament comes to its clearest and fullest expression in God's covenant with Abraham (see Gen. 12:1-3; 17:1-14). This covenant may be summarized in the words of Genesis 17:7, "I will establish my covenant between me and thee and thy seed after thee in their generations for an everlasting covenant, to be a God unto thee, and to thy seed after thee." In this covenant God is more specific as to the blessings that he will give. In this covenant, too, faith suddenly becomes more prominent as the condition which man must meet if he is to receive the promised blessings.
The blessings that God promised Abraham in this covenant were both temporal and spiritual, earthly and heavenly, external and internal. Abraham's temporal or earthly blessings consisted in a "seed," a "land," and in the promise that he would be the father of "a great nation." These promises were partly fulfilled in the giving of Isaac as the son of Abraham's old age, in bringing Abraham to the land of Canaan, and in making Abraham the father of the mighty Hebrew nation. It would be a serious error, however, to maintain that these temporal blessings of Abraham stand in contrast to the spiritual blessings of salvation in Christ. Bound up in these very earthly blessings were heavenly blessings. While "in the land of promise, as a strange country, dwelling in tabernacles," Abraham looked beyond this earthly land "for a city which hath foundations, whose builder and maker is God," even the heavenly and eternal Jerusalem (see Heb. 11:9-10). What is more, the true Seed of Abraham through which all the families of the earth would be blessed was not the Hebrew nation but Christ. Paul, writing to the Galatians, said, "Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ." The blessings that God promised would come through the seed of Abraham were not essentially material blessings but the blessings of eternal salvation through the Lord Jesus Christ.
Not only were there heavenly and spiritual blessings bound up in the earthly and external blessings given to Abraham; at the very heart and center of God's covenant with Abraham was the promise of reconciliation and salvation. The most important element of God's Covenant with Abraham was the promise to "be a God unto thee, and to thy seed after thee." This is the blessing without which all other blessings would be empty and worthless. God was at enmity with man because of man's rebellious unbelief and disobedience. God in his justice had placed all mankind under his holy curse. He had cut man off from himself. But now he will become reconciled to man and deal with him as a friend. "I will be thy God and thou shalt be my people" is the echo that reverberates through the Old Testament. He will restore man into his favor and fellowship once more. He will save men through his Son, "that the blessing of Abraham might come on the Gentiles through Jesus Christ" (Gal. 3:14). To that appointed Savior all the believers of the Old Testament looked for salvation and by that promised One they were saved. In the words of our Lord, "Your father Abraham rejoiced to see my day; and he saw it and was glad" (John 8:56).
There was one essential condition—and only one—that must be met if Abraham were to receive the promised temporal and spiritual blessings. Abraham must believe; he must have faith. This one condition Abraham met and by it laid hold upon the blessings of salvation in Christ. "Abraham believed God and it was accounted to him for righteousness" (Gal. 3:8; Rom. 4:3). Abraham believed that God would keep his promises, and thus he was regarded as righteous in God's sight.
God gave an external sign to Abraham to keep Israel in remembrance of this covenant and to confirm all he had said. Under the Old Testament administration of the covenant of grace all the male members of the covenant were to receive "the sign of circumcision, a seal of the righteousness of faith" (Rom. 4:11). Later, the sign of baptism as a seal of the new covenant of grace was to supplant the sign of circumcision (see Col. 2:11-12).
This glorious covenant of grace that God made with Abraham was never revoked. It was never supplanted by another covenant. God was to add to this covenant but never to subtract from it. God was to unfold the meaning of this covenant more fully but never to change it essentially.
From Moses to Christ
As the history of God's people progressed, God added to the covenant of grace the law. This law was revealed to Moses on Mount Sinai and occupies a prominent place throughout the entire Old Testament (see Ex. 19:16 through Leviticus). It should be made very clear that God did not do away with the covenant of grace when he gave the law. The law is not a substitute for grace. God did not intend that thenceforth man was to be saved by keeping the law. "By the works of the law shall no flesh be justified" (Gal. 2:16). The law was added simply as a means of administering the covenant of grace more effectively. "The law was added because of transgressions" (Gal. 3:19). "By the law is the knowledge of sin" (Rom. 3:30). These words of the apostle Paul make clear what the purpose of the law was. The purpose of the law was to increase Israel's sense of sin and thereby bring them to see their need of a Savior.
The laws by which the covenant of grace was administered from the time of Moses to the coming of Christ were of three different types. They were the ceremonial law, the civil law, and the moral law.
The ceremonial law, as set forth in the book of Leviticus, was composed of numerous symbols and types. A symbol is a material representation of some spiritual truth. A type is a symbol intended to foreshadow something that is to come in the future. The tabernacle was a perfect symbol and type of the work of Christ as the Mediator between God and man. The heart of the tabernacle was the Holy of Holies. Once a year on the Day of Atonement, the high priest entered the Holy of Holies and sprinkled the blood of a goat upon the mercy seat to make atonement for the sins of the people of Israel. The high priest placed his hands on the head of another goat and confessed the sins of the people of Israel. The goat was then driven forth into the wilderness (symbolic of the taking away of their sins; cf. Lev. 16; 23:26-32; Num. 29:7-11). The epistle to the Hebrews makes it very plain that this ceremony on the Day of Atonement foreshadowed the entrance of Jesus, the great high priest, once for all "into heaven itself, now to appear in the presence of God for us" (Heb. 9:24; cf. 9:1ff.). Through Christ's sacrifice on the cross we come into the Holy of Holies of God's presence. These Old Testament ceremonies were done away with in Christ. They were but shadows of things to come. When Christ came, there was no longer any need for these types and shadows. He was the fulfillment of them. This is the main burden of the epistle to the Hebrews.
The civil law was that part of God's law that was to govern Israel as a nation and society. The civil law was the application of the moral law to the social and civil life of Israel. Israel was a theocracy (ruled by God). The laws of sanitation, for instance, were revealed by God and made binding on the people of Israel. These civil laws tended to emphasize the national, temporal, and external aspects of the covenant. God stood in covenant relation to Israel as a Jewish nation. Temporal or material blessings such as the promise of the land of Canaan are quite prominent. There is also an emphasis on external washings and observances. When Israel as a nation rejected their Messiah and the kingdom of God was offered to the Gentiles, Israel as a theocratic nation governed by the civil laws of Sinai was no more. Therefore, these civil laws are no longer binding, "further than the general equity thereof may require" (as stated by the Westminster divines; see also 1 Cor. 9:7-10).
There was one aspect of the law revealed at Mount Sinai that was never to pass away. That was the moral law summarized in the ten commandments. In the moral law is revealed man's duty to God and to his neighbor. The moral law has the same functions today that it did in the time of Moses. It is still God's means to convict men of their sin and to show them their need of a Savior. It still remains as a standard of conduct after we have accepted Christ as our Savior. Christ delivers men from the curse of the law (Gal. 3:13) but not from the moral obligation to keep the law as an expression of faith in and love for Christ. When a lawyer came to Jesus seeking eternal life, Jesus confronted him with a summary of the Ten Commandments to convict him of his sin (see Luke 10:25-28). Paul in writing to the Christians at Rome set forth the commandments of the Old Testament as the guide and standard for Christian conduct (see Rom. 3:31, 6:15, 13:9).
From www.opc.org