Creation ordinances largely make up the content (or at least context) of the Old Covenant. Robertson comments: "The covenantal relation established by creation permeates the whole history of God's forming a people for himself." Whatever hierarchy, stipulations, sanctions, and continuities that were set up before the fall continue in effect afterwards, but in the sphere of death and decay. God now is offended by Adam, because of his rebellion, and thus His blessed presence can only bring curse. Adam must be driven away from God's presence.
What God does to rectify this situation is to redeem man by a promised Seed, and He sets up an administration to bring this Seed to save man. Faith in this coming Seed will be a constant requirement of each Old Covenant administration, and the coming Seed will be portrayed in more or less typological and shadowy ways.
Discontinuity within the Old Covenant administrations can largely be attributed to the growth and development of humanity through God's providential plan. While New Covenant discontinuity with the Old can be explained in this way also, the centralizing aspect of that development is the new status of Man fulfilled in the resurrected seed, Jesus Christ. Types and shadows fall away to be revealed in the person of Christ, the Seed, the Melchizedekian priest, the new Holy Land of our incorporation.
The covenant made with Abraham is God's beginning fulfillment of His promise to bring a Seed to crush the head of the serpent, and rescue man from his fallen condition. As such, it is worthy of particular attention to see how much of it remains continuous with subsequent covenants in the Old Covenant period, and to compare it to the fulfillment of the promise in the New.
After the Flood, humanity attempts to create their own central sanctuary at Babel. They disobey God's command to fill the earth, and they attempt to seize sanctuary privileges for themselves by building a tower to heaven (Genesis 11:4). God frustrates these designs: His intention is to call a seed-people and set them in a sanctuary land himself.
Abram is called from a dire situation. He lives in Ur of the Chaldees. Joshua 24:2 indicates that idolatry had crept in to the line of Shem, and Abram lived in a civilization under judgment for idolatry. There was only death and barrenness for him in that land. His brother Haran died while their father was still alive, which is a reversal of usual expectation. Further, Abram's wife Sarai is barren. Abram's father takes them out of this to Canaan, to a place called Haran, and there dies as well (Genesis 11:26ff). Things do not look good for Abram's family at all, but God graciously calls him out of this, and promises to lead him to a new country, and to make of him a great nation.
God calls to Himself a priestly nation, and enforces the distinction by means of boundaries, both physical (the land) and sacramental (circumcision).We may understand this covenantal act by relating it to God's creational acts: God separates waters into waters above and waters below, and does so by means of a mediatorial boundary. What was there before was water, and after the separation there is still water, yet in two different places and separated. There is continuity with the past, and also discontinuity.
Abraham is called from a Noachic context, and is under Noachic ethical stipulations. The inscripturated revelation of the Noachic covenantal stipulations is sparse, however. Primary is the new sanction against murder, the permission to eat all flesh, and the prohibition on drinking any blood (Genesis 9:1-7). But other stipulations seem to be understood, such as the weekly Sabbath, some sacrificial regulation, the clean/unclean distinction (though any animal was permissible to eat) and so forth. These may be understood as postlapsarian creational ordinances. Thus again, there is continuity to this past, and restoration of continuity with the pre-flood world with a central sanctuary-land for the priestly line.
For Aaron, he is constituted by the meta-priest, meta-mediator Moses. For Abraham, who is the beginning of the entire Levitical priestly system, his priesthood is blessed by a greater priesthood, that of Melchizedek. This has obvious reference to the New Covenant, as the Epistle to the Hebrews makes clear.
Once in the land, Abram is promised it as a perpetual inheritance. But it's borders face invasion from Chedolaomer. Abram defeats Chedolaomer, and at this point (Genesis 14:17-18) we learn of Melchizedek, who brings forth bread and wine (a sacramental act) and blesses Abraham (and the priestly system nascent in his loins). Calvin remarks:
For seeing that the holy patriarch who God had raised to the highest rank of honor submitted himself to Melchizedek, it is not to be doubted that God had constituted him the only head of the whole church; for, without controversy, the solemn act of benediction, which Melchizedek assumed to himself was a symbol of preeminent dignity.
Melchizedek is present as meta-priest to the seed-priest. Blessing comes to all the seed of Abraham through Melchizedek. The typical blessing of the covenant is presence within the borders of the land of Canaan. But Melchizedek's blessing transcends the land-orientation, and as such is an "intrusion" of new covenant grace.
After the meeting with Melchizedek, Abram apparently fears another invasion of the land. At this point God makes His covenant with Abraham, binding himself to provide both a seed to inherit and a land of inheritance. Melchizedek functions to provide the non-typical proleptic New Covenant blessing that is the only anticipatory basis for which God can make promises within the death-ministering Old Covenant. Isaac is not The Seed; truly, Christ is (Galatians 3:16). Aaron is not the True Priest, Christ is (Psalm 110:14). David is not the true High King of Israel, Christ is (Psalm 110:1).
Melchizedek is a Noachic priest-king, and typical of Christ. Thus we should not be surprised to find that because of his mediatorial work, the Noachic covenant and the Abrahamic that follows it are composed of many more continuous elements than later more typical Mosaic legislation. Ethical Stipulations of the Abrahamic Covenant. Abram was bound to keep whatever law God had revealed to him, which for him was that of the Noachic instruction. Abram thus legitimately made war against those who shed man's blood. He also could eat of every animal, whether clean or unclean.
But several new duties entered in with the covenant. Abraham was required to circumcise his male offspring and servants. He was likely restricted in which animals he could now offer to God. (While Noah sacrificed every clean beast (sheep, oxen, gazelles, chickens, etc.) the covenant that God makes with Abraham involves the five animals that God later specifies as the only ones that may be brought near to His altar.) Abraham is said by God to have "kept my charge, my commandments, my statutes, and my laws," (Genesis 26:5) an inclusive statement that likely involves a great deal of detail.
As the Abrahamic covenant progresses through to the lives of Jacob and his children, we see other applications of what is later set down only in the Mosaic revelation. The requirement of marriage for seduction is seen in Genesis 34. The Levirate law is seen operating in Genesis 38.
The pericope of Leviticus 17-22 contains warnings of the judgment that came upon the Canaanites for committing abominations in the Land. Also stipulations are given that are said to apply equally to Israelites and to strangers who dwell in the land. Further it is here that the Noachic prohibition against blood drinking is reiterated. For these reasons, much of this pericope may likely be understood to be of abiding validity backwards to Abraham also.
The question might then be raised about Abraham's marriage to his sister (the daughter of his father). If it was permissible for Abraham to do so, and for others who lived in his period, why is it later classified as an abomination for which the Canaanites are being vomited out. Perhaps this is an indication that Leviticus 17-22 should not be understood as operative in the Abrahamic period. This is initially plausible as an interpretation of the statement that the iniquity of the Amorites was not yet full (Genesis 15:16); i.e., God's new requirements to Israel were not operative until He gave them in Leviticus, and then the Canaanites are vomited out in accordance with them. But this must be rejected because it portrays God judging the Canaanites for violating requirements of which they were unaware.
Another suggestion might be that the statement that the Canaanites were being judged for "all these abominations" should just not be taken as inclusive of the one prohibition on sister-marriage. It is possible to take this as an "agnostic" answer to the issue. But it might not be necessary.
The answer would seem to be that Abram's marriage to Sarai was permitted as an expression of the Noachic stipulations. (Although, even here, the race could be propagated from Noah's sons without violating Leviticus 18; there is no prohibition on cousins marrying in that passage.) With the entrance of the Abrahamic covenant, then, such union would be understood to be forbidden. On this basis the Canaanites may be justly vomited out for breaking all of the specified sins of Leviticus 18. Further, Jacob's taking a second wife, sister of the first, (compare Leviticus 18:18) is more clearly a sinful act (though the strife that the act caused has usually been understood as indicative of its ill-advisability).
The section begins in discontinuity, however, with a new regulation related to the presence of a new thing: the tabernacle of God in the presence of His people. No longer may the Israelites offer sacrifices to God in any place as they did previously. This serves the interest of the unity of God's people in worship. Further, God restricts any killing of animals even to eat without offering them as a sacrifice to the Lord, lest the people (here Israelite or gentile) surreptitiously make demonic sacrifices (Leviticus 17:7).
Then the stipulations reiterate some of the Noachic legislation, prohibiting the drinking of blood, not solely because the life is in the blood, but because blood it that which is set up to make atonement (as the preceding chapters of Leviticus discuss in detail). Also, Israelites and gentiles have to drain the blood from any animal that they do eat.
Then follows a whole section enumerating abominable sexual practices, which apply to Israelite and gentile alike. These practices are referenced as being those which the Canaanites practiced, and for which they were spewed out. Other things are included as well, such as Molech worship. These statements are reiterated in Leviticus 20, with sanctions attached.
There is a covenantal structure to the passage overall, relating to this new situation: the coming of a new law that overwrites previous legislation and spews out paganism. Emphasis is placed not just on not practicing these things, but on rejection of the Canaanitish law-system 18:3-5, 30; 20:22-23. The law comes as gracious defeat of Israel's enemies. The five-part structure is followed, particularly with reference to the double-fives of the decalogue.
Understanding the origin of these stipulations of the council in Leviticus may illuminate the issue of ethical continuity for New Covenant saints. "Meats offered to idols" should be understood as referring to participating in pagan worship as such, not (as Paul permits) eating that which is sold in markets. "Fornication" may be filled out in greater detail, and provide a clear basis for continuing to condemn homosexual union (without having to answer charges that this is some sort of abrogated ceremonial prohibition).
Not all questions are answered, though. John Owen indicates that this advice of the council is limited to the New Testamental period, when the Jews and Gentiles were still being integrated into one church. Questions also might remain about what constitutes blood-drinking and whether "kosher-killing" methods are mandatory today, or whether only more extreme forms of blood drinking are under consideration.
Jordan, James B., Covenant Sequence in Leviticus & Deuteronomy, Tyler, TX: The Institute for Christian Economics, 1989.
Owen, John, An Exposition to the Epistle to the Hebrews, Vol. 5, Edinburgh, The Banner of Truth Trust, 1991.
Robertson, O. Palmer, The Christ of the Covenants, Phillipsbugh, NJ: Presbyterian and Reformed Publishing Co., 1980.
Wenham G. J., The Book of Leviticus, Grand Rapids: Eerdmans, 1979.
Sutton, Ray R., That You May Prosper, Tyler, TX: The Institute for Christian Economics, 1987.
 O. Palmer Robertson, The Christ of the Covenants, (Phillipsbugh, NJ, Presbyterian and Reformed Publishing, 1980), p. 45
 G. J. Wenham, The Book of Leviticus, (Grand Rapids, Eerdmans, 1979), p. 132. Also compare Exodus 4:16 and Zechariah 3:1-8
 John Calvin, Commentary on the First Book of Moses called Genesis, (Grand Rapids, Baker Book House, 1989), pp. 386-387.
 I note in passing that R. J. Rushdoony's opinion that parent/child incest, as well as brother/sister incest makes this question even more problematic, as then the Canaanites are being vomited out for even less of the stated grounds of Leviticus 18 and 20.
 Another gentile-inclusive aspect of the Abrahamic covenant is circumcision, which is administered to nongenealogical household servants as well as children.
 James B. Jordan, Covenant Sequence in Leviticus & Deuteronomy, (Tyler, TX, The Institute for Christian Economics, 1989), pp. 33-36
 Ray R. Sutton, That You May Prosper, (Tyler, TX, The Institute for Christian Economics, 1987), pp. 214-224.
 Jordan, op. cit.
 John Owen, An Exposition to the Epistle to the Hebrews, Vol. 5, (Edinburgh, The Banner of Truth Trust, 1991), pp.323-324.