Two Abrahamic Covenants?
To make things a little more tricky, some scholars claim to see not one but two covenants made with Abraham by the Lord. This is the position of Paul Williamson as set out in his fine book Sealed with an Oath. Williamson believes that the thirteen year time lapse between Genesis 15 and 17, plus what he calls “significant differences…in terms of their covenantal framework and their promissory emphases” argue for two covenants.
But the time gap is not in itself a problem for a Divine covenant. Clearly it would take many generations for the descendants to appear. The issue is really over the repetition of covenantal language and what receives emphasis. What it boils down to for the two covenant view is that Genesis 15 is said to be temporal and unilateral, whereas Genesis 17 is eternal and bilateral. Williamson sees the two covenants with Abraham as stemming from “the two separate strands set out in the programmatic agenda of Genesis 12:1-3.”
It is of little moment to the overall thesis of this book to have to decide whether Williamson is right. But the two strands, which are certainly present, seem too interrelated to prise apart. In Genesis 15 the seed promise is followed, naturally enough, by the land promise. The one involves the other. The boundaries of the land given to Abraham’s descendants (through Isaac and Jacob) are for Israel. The international aspects of the promise are for Israel and the Nations through Messiah. It is Williamson’s supercessionism which appears to force him to stress the national/international paradox the way he does.
Also, as I have shown above, the token of circumcision is not part of the covenant oath. Moreover, circumcision pertains to the physical descendants who will be given the land, so the reasons which are adduced for separating Genesis 15 and 17 into two covenants become very strained. Even scholars who are sympathetic to Williamson’s supercessionist approach have not been persuaded by his arguments. And when we look at later events it becomes even more difficult to try to keep apart what the narrative seems to want us to take together. It is better, therefore, to understand chapter 17 as providing further complementary revelation on the covenant God cut in chapter 15.
God’s “No” to Ishmael
Moving on to the second half of Genesis 17 (vv.15-22), we encounter Abraham’s advocacy for his son Ishmael. The patriarch is anxious that his son not be excluded from the blessing of God. It will help if we print the text below:
Then God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name. 16 “And I will bless her and also give you a son by her; then I will bless her, and she shall be a mother of nations; kings of peoples shall be from her.”
17 Then Abraham fell on his face and laughed, and said in his heart, “Shall a child be born to a man who is one hundred years old? And shall Sarah, who is ninety years old, bear a child?”
18 And Abraham said to God, “Oh, that Ishmael might live before You!”
19 Then God said: “No, Sarah your wife shall bear you a son, and you shall call his name Isaac; I will establish My covenant with him for an everlasting covenant, and with his descendants after him.
20 “And as for Ishmael, I have heard you. Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly. He shall beget twelve princes, and I will make him a great nation.
21 “But My covenant I will establish with Isaac, whom Sarah shall bear to you at this set time next year.”
22 Then He finished talking with him, and God went up from Abraham – Genesis 17:15-22
The whole episode is very clear. For all his father’s urgent pleading on his behalf, Ishmael is not and will not be a party to the covenant. Despite the clear declaration of God that the covenant is established through Isaac and not Ishmael, it is surprising how many Bible readers miss this.
Nevertheless, the passage indicates that Ishmael is the recipient of Divine promises (cf. 21:13, 18). This is proof that we should not treat automatically covenants and promises as if they were the same thing. As it concerns the Abrahamic covenant, we should note that the national and land aspects of the covenant are just as particular (more so in the OT) as the international aspects (which become clearer as we draw towards the NT). In the Pentateuch, the narrative will concentrate on the seed promise, and the land will never be far out of view.
This passage (Genesis 17:15ff.), is a locus classicus to prove that there is a difference between a promise and a covenant. Covenants establish some kind of relationship between the parties, whereas promises do not necessarily include relationships. Covenants are oath-bound, whereas promises are not. Theologically speaking, covenants are strongly implicative, whereas promises may carry little or no future repercussions for the biblical storyline.
 Paul R. Williamson, Sealed with an Oath, 86
 Williamson notes a few other matters such as the international extent of the Genesis 17 promises. Ibid, 87
 Ibid, 89
 See the discussion in Kenneth A. Mathews, Genesis 11:27 – 50:26, 195-199.
 Just a few examples would be Genesis 28:4; 35:10-12, and Ezekiel 34:11-15
 See Sailhamer, Meaning of the Pentateuch, 433