Galatians 4:23

But the son by the slave was born according to the flesh, and the son by the free woman through the promise.

By faith Sarah herself received power to conceive, even when she was past the age, because she considered him faithful who had promised.

nor are they all children of Abraham because they are his descendants; but, "Through Isaac shall your descendants be named."

In hope, he believed against hope, so that he became the father of many nations; as he had been told, "So shall your descendants be."

But what does it say? "The word is near you, in your mouth and in your heart" (that is, the word of faith which we preach);

Now you, brethren, like Isaac, are children of promise.

Treasury of Scripture Knowledge

But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise.

nor are they all children of Abraham because they are his descendants; but, "Through Isaac shall your descendants be named."

In hope, he believed against hope, so that he became the father of many nations; as he had been told, "So shall your descendants be."

But what does it say? "The word is near you, in your mouth and in your heart" (that is, the word of faith which we preach);

By faith Sarah herself received power to conceive, even when she was past the age, because she considered him faithful who had promised.

Now you, brethren, like Isaac, are children of promise.