WE ARE NOT TO THINK that God disclosed himself to Abram every day: the decisive moments take place over considerable time. Putting the chronological hints together, Genesis 12 occurs when Abram is seventy-five; Genesis 15 is undated, but occurs during the following decade. Now he is ninety-nine, and Ishmael is already thirteen (Gen. 17:1, 25). God’s opening words on this occasion must have been a great comfort, pulling together as they do some of the themes already introduced: “I am God Almighty; walk before me and be blameless. I will confirm my covenant between me and you and will greatly increase your numbers” (17:1-2).
In the following verses, there is initial emphasis on the covenant, on the promise of the land, and on the fact that Abram will be “the father of many nations” (17:4-5). The latter takes pride of place, but there are three new elements that carry the history of redemption forward.
First, both Abram and Sarai are given new names. If Abram means “exalted father,” Abraham means “father of many,” i.e., “the father of many nations,” which implicitly announces that however important his role as head of the fledgling Hebrew nation, Abraham will be greater still in his foundational role as the one through whom all the peoples of the earth will be blessed (12:3). Sarah “will be the mother of nations” (17:16).
Second, God introduces circumcision as the initiatory sign of the covenant. Circumcision was practiced by several ancient Near Eastern peoples. Here, however, it has a distinctive role: a rite that is not unknown in Abraham’s world is picked up by God and assigned distinctive significance in the history of the covenant God enters into with his people. Abraham loses no time in complying (17:23-27). This is a social “boundary marker” which across the course of history increasingly marks the Hebrews out as different; but it is more than that. It is so definitively established as the unique sign of the everlasting covenant that failure to comply means one is cut off from the people of God (17:13-14). Even before there is a great quantity of stipulation in the covenant, its framework, its boundary, and its symbolism are being established.
Third, Abraham’s understandable but unhappy skepticism that he will bring forth a son of Sarah at this late stage in their marriage leads him to propose Ishmael as the one through whom God will fulfill his promises (17:17-18). But God will have none of it. Ishmael will sire great numbers, but the covenant line goes through Isaac (17:19-21). The history of the covenant people is thus decisively shaped by God’s sovereign choice.