Throughout Genesis 12-17, God makes promises to Abraham’s descendents. A question that divides theologians is this: Who are the descendents of Abraham, that is, who will inherit the promises to Abraham?
Dispensationalists argue that the descendents of Abraham are his physical offspring, those who are related to Abraham by blood. Thus, the promises are made to Abraham’s physical children.
Covenant Theologians argue that the descendents of Abraham are his spiritual offspring, those who are related to Abraham by faith. Thus, the promises are made to Abraham’s spiritual children.
In examining this issue, we must recognize that not all of Abraham’s physical descendents will inherit the promises. Even though God uses universal language, such as “To your descendents I will give this land” (Gen 12:7), God never intended this to mean every single one of Abraham’s children.
Abraham asked God to include Ishmael, but God replied, “As for Ishmael, I have heard you. Behold, I have blessed him … but my covenant I will establish with Isaac” (Gen 17:20-21). So, the descendents of Abraham through Ishmael are not included in the promises; only the descendents of Abraham through Isaac are included in the promises.
Also, Abraham had six sons with his second wife, Keturah, yet none of these are included in the promises. Thus, out of Abraham’s eight sons, only Isaac is included in the promises. In fact, Isaac is Abraham’s “only son” according to God (Gen 22:2).
Additionally, God again narrowed the promise to the line of Jacob. Esau and his descendents (Edomites) are not included in the promises. Though the Edomites are ethnic descendents of Abraham, they are not considered “descendents” with respect to the promises.
God allowed for the further contraction of Abraham’s “descendents.” “The uncircumcised male child, who is not circumcised in the flesh of his foreskin, that person shall be cut off from his people; he has broken My covenant” (Gen 17:14). An ethnic descendent of Abraham who was not circumcised was not considered a descendent of the promises. Thus, physical descent alone does not make someone a “descendent” of Abraham.
Furthermore, God allowed for the expansion of Abraham’s “descendents” to include those not related to Abraham by blood. When God instituted circumcision, Abraham was to circumcise not only his physical children, but also male children who are “bought with money from any foreigner who is not your descendent” (Gen 17:12). That is, a foreigner who was circumcised became a descendent of Abraham.
Thus, the picture that we get from the OT is that the descendents of Abraham, those who would inherit the promises, were initially comprised of Jacob’s physical descendents, minus those who were not circumcised, plus those foreigners who were circumcised.
We later learn that although physical circumcision was important and was required for entrance into the covenant, what God really wanted was spiritual circumcision (Jer 4:4). In fact, those who were physically circumcised but not spiritually circumcised were cut off. Thus, God’s promises were not necessarily to those who shared Abraham’s bloodline, but to those who shared Abraham’s faith. God’s promises were to the spiritual descendents of Abraham.
As Israel departs from Egypt, a “mixed multitude” went with them (Ex 12:38), which included Egyptians and other nationalities. These foreigners became Israelites.
We also have several examples of foreigners becoming Jews. Prominently, two foreign women not only become Jews but married into the line of David. Rahab was a Canaanite harlot, who became the mother of Boaz. Ruth was a Moabite, who married Boaz and became the great-grandmother of David. So, David was one-eighth Moabite and one-sixteenth Canaanite.
So, according to the OT, the heirs of the promises to Abraham are his spiritual descendents. This is spelled out even more clearly in the NT, which we will look at next.