But it is not that the word of God has failed. For not all who are of Israel are Israel, nor are they all children of Abraham because they are his descendants; but “It is through Isaac that descendants shall bear your name.” This means that it is not the children of the flesh who are the children of God, but the children of the promise are counted as descendants. For this is the wording of the promise, “About this time I shall return and Sarah will have a son.” And not only that, but also...