6 The promises were spoken to Abraham and to his seed. The Scripture does not say “and to seeds,” meaning many people, but “and to your seed,” meaning one person, who is Christ. 17 What I mean is this: The law, introduced 430 years later, does not set aside the covenant previously established by God and thus do away with the promise. 18 For if the inheritance depends on the law, then it no longer depends on a promise; but God in his grace gave it to Abraham through a promise. (Galatians 3:16-18)

10 Yet it was the LORD’s will to crush him and cause him to suffer,
and though the LORD makes his
life a guilt offering,
he will see his offspring and prolong his days,
and the will of the LORD will prosper in his hand. (Isaiah 53:10)

8 Produce fruit in keeping with repentance. And do not begin to say to yourselves, ‘We have Abraham as our father.’ For I tell you that out of these stones God can raise up children for Abraham. (Luke 3:8)

8 A man is not a Jew if he is only one outwardly, nor is circumcision merely outward and physical. 29 No, a man is a Jew if he is one inwardly; and circumcision is circumcision of the heart, by the Spirit, not by the written code. Such a man’s praise is not from men, but from God. (Romans 2:28-9)

6 It is not as though God’s word had failed. For not all who are descended from Israel are Israel. 7 Nor because they are his descendants are they all Abraham’s children. On the contrary, “It is through Isaac that your offspring will be reckoned.” 8 In other words, it is not the natural children who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring. (Romans 9:6-8)