Verses 28-30 of Paul’s allegory is based on Genesis 21:9-10. Isaac was continually persecuted by his older half brother Ishmael. Eventually, Ishmael and his mother Hagar were expelled because Ishmael had no standing in God’s eyes as heir of Abraham. Just like Isaac, the New Testament saints were children of promise. Just as Isaac was subject to Ishmael’s persecution (see Gen. 21:9), so the early Christians were subject to persecution from the legalists. By applying this quote from Genesis 21:10, Paul commands the Galatians to get rid of the legalizers. Their work does not have the authority or blessing of God. It must come to an end. The Galatians must choose to be free and act on that choice by expelling the Judaizers.

In creating a parallel between the story from Genesis and the Galatians’ situation, Paul points out that (1) the persecution by the Jewish legalists of his day was not unexpected, and (2) it would not go on indefinitely because the legalists would soon be cast out.

In applying the truth from the biblical illustration, Paul made three comparisons, as we will see shortly.