²³ His son by the slave woman was born according to the flesh,^(A) but his son by the free woman was born as the result of a divine promise.^(B)

¹¹ And by faith even Sarah, who was past childbearing age,^(A) was enabled to bear children^(B) because she^[a] considered him faithful^(C) who had made the promise.

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.”^{[a](A) 8} In other words, it is not the children by physical descent who are God’s children,^(B) but it is the children of the promise who are regarded as Abraham’s offspring.^(C)

²⁸ Now you, brothers and sisters, like Isaac, are children of promise.^{(A) 29} At that time the son born according to the flesh^(B) persecuted the son born by the power of the Spirit.^(C) It is the same now.

The Birth of Isaac

21 Now the Lord was gracious to Sarah^(A) as he had said, and the Lord did for Sarah what he had promised.^{(B) 2} Sarah became pregnant and bore a son^(C) to Abraham in his old age,^(D) at the very time God had promised him.^(E)