What Does Galatians 4:28 Mean?

Now we, brethren, as Isaac was, are the children of promise. Paul applies the allegory directly. "Now we" (hēmeis de, ἡμεῖς δέ)—we believers, both Jewish and Gentile Christians. "Brethren" (adelphoi, ἀδελφοί)—fellow believers. "As Isaac was" (kata Isaak, κατὰ Ἰσαάκ)—according to the pattern of Isaac, in the same category as Isaac. "Are the children of promise" (epangelias tekna esmen, ἐπαγγελίας τέκνα ἐσμέν)—we are promise-children, not flesh-children.

Our spiritual identity corresponds to Isaac: born by supernatural divine power in fulfillment of divine promise, received through faith when natural possibility was dead. We're not Ishmael-type (born of human effort, natural ability, works of flesh). Our birth into God's family came through believing God's promise of salvation in Christ, accomplished by the Spirit's regenerating power. This is true of every Christian, regardless of ethnic background. Law-observers are Ishmael's children; faith-believers are Isaac's children. The Judaizers had it backwards: they thought circumcision made them Isaac's children. Paul shows faith alone does.