Untitled Sermon (2)
8. It is not the children of the flesh who are the children of God, but the children of the promise are reckoned as descendants. The ‘children of the promise’ in Paul’s exegesis are those who, like Abraham, believe the promise of God and are therefore Abraham’s spiritual offspring. Compare 4:11–18, and also the ‘allegory’ which Paul draws out of the Isaac-Ishmael narrative in Galatians 4:22–31.
9. ‘About this time I will return and Sarah shall have a son.’ A quotation from Genesis 18:10, ‘I will surely return to you in the spring, and Sarah your wife shall have a son.’ This was the ‘promise’ in accordance with which Isaac was born—the promise which provoked Sarah to laughter (Gen. 18:12; cf. 21:6).