Romans 9:6-8

Amplified Bible, Classic Edition

⁶ However, it is not as though God’s Word had failed [coming to nothing]. For it is not everybody who is a descendant of Jacob (Israel) who belongs to [the true] Israel.

⁷ And they are not all the children of Abraham because they are by blood his descendants. No, [the promise was] Your descendants will be called and counted through the line of Isaac [though Abraham had an older son].^(A)

⁸ That is to say, it is not the children of the body [of Abraham] who are made God’s children, but it is the offspring to whom the promise applies that shall be counted [as Abraham’s true] descendants.