Romans 9:7-9

Amplified Bible

⁷ 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].^{(A) 8} 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. ⁹ For this is what the promise said: “About this time [next year] I will come, and Sarah shall have a son.”^(B)