Romans 9:6-11

However, it is not as though God’s word has failed [coming to nothing]. For not all who are descended from Israel (Jacob) are [the true] Israel; and they are not all the children of Abraham because they are his descendants [by blood], but [the promise was]: “YOUR DESCENDANTS WILL BE NAMED THROUGH ISAAC” [though Abraham had other sons]. [Gen 21:9-12] That is, it is not the children of the body [Abraham’s natural descendants] who are God’s children, but it is the children of the promise who are counted as [Abraham’s true] descendants. For this is what the promise said: “ABOUT THIS TIME [next year] I WILL COME, AND SARAH SHALL HAVE A SON.” [Gen 18:10] And not only that, but this too: Rebekah conceived twin sons by one man [under the same circumstances], by our father Isaac; and though the twins were not yet born and had not done anything either good or bad, so that God’s purpose [His choice, His election] would stand, not because of works [done by either child], but because of [the plan of] Him who calls them