Today’s reading: Genesis 16-18
…your wife Sarah will bear you a son, and you will call him Isaac. I will establish my covenant with him as an everlasting covenant… Genesis 17:19
Through years of waiting for God to fulfill his promise of a son, Abram struggles between keeping faith and taking action himself. Ten years after the promise is given, Abram and Sarai conspire together to produce a child through their maid, Hagar. The plan is unfaithful in every way and produces a son, Ishmael, who brings conflict, not blessing, into the family. Thirteen years after Ishmael’s birth the promised child is finally born to Sarai, now called Sarah, and Abram, now called Abraham. God changes their names to match the reality of their new roles as mother and father of a nation of kings and priests.
God makes a tremendous distinction between Ishmael and Isaac. He tells Abraham, “my covenant I will establish with Isaac.” A few years later, speaking to Abraham about Isaac, God calls him “your son, your only son, Isaac, whom you love.” If there was any doubt about why God insisted on fulfilling his plan through Isaac, the apostle Paul made it plain in the book of Romans:
In other words, it is not the children by physical descent who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring. Romans 9:8
We attempt and sometimes accomplish much by our own strength, but God has ordained that only the things which are done through his power will have lasting significance. Only his strength working in and through believers will produce eternal benefits. Isaac is a miracle child born to impossibly old parents. His birth is supernatural, and God uses the supernatural to accomplish his will.
Since Ishmael therefore was excluded from participating in the covenant grace, which was ensured to Isaac alone; and yet Abraham was to become a multitude of nations, and that through Sarah, who was to become “nations” through the son she was to bear (Genesis 17:16); the “multitude of nations” could not include either the Ishmaelites or the tribes descended from the sons of Keturah (Genesis 25:2.), but the descendants of Isaac alone; and as one of Isaac’s two sons received no part of the covenant promise, the descendants of Jacob alone. But the whole of the twelve sons of Jacob founded only the one nation of Israel, with which Jehovah established the covenant made with Abraham (Ex 6 and 20-24), so that Abraham became through Israel the lineal father of one nation only. From this it necessarily follows, that the posterity of Abraham, which was to expand into a multitude of nations, extends beyond this one lineal posterity, and embraces the spiritual posterity also, i.e., all nations who are grafted into the seed of Abraham (Romans 4:11-12, and Romans 4:16, Romans 4:17). – Keil & Delitzsch Commentary on the Old Testament
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