6.10 Galatians -- Two Covenants
Paul closes chapter 4 with a complex analogy drawn from the Old Testament. He is contrasting the Judaizers with the true Christians. The representatives of each side are:
Ishmael -- Hagar -- Mt Sinai -- Jerusalem -- Old Covenant -- born of flesh
Isaac -- Sarah -- _______ -- Jerusalem above -- New Covenant -- born of Spirit -- children of promise
This is a bit messy, because the pairs are unequal. Nevertheless, his meaning is plain, and bold:
"the present city of Jerusalem... is in slavery with her children (Gal 4:25)."
Those who still follow the Old Covenant, and this includes his opponents, the Judaizers, will not inherit the Kingdom that belongs to the sons of Abraham. In a sense, he is turning the weapon of the Judaizers upon themselves. "You want the Old Testament? Here, I give you the heart of it -- and by it you are condemned!"