Having examined the differences between typology and allegory, it remains for us to look at Paul’s application of the Hagar and Sarah typology to the Christian life (Gal. 4:21–31). Note first that the apostle’s use of this story from Genesis 16 and 21:8–21 is probably a response to its abuse by the Judaizers in Galatia. In all likelihood, the false teachers looked to Hagar to prove their case for circumcision, telling the Gentile Christians in Galatia that they risked being cast out of the redeemed community like Abraham’s Gentile maid-servant and son if they did not add the practices of the Jewish law to their Christian faith.
This interpretation was based on a superficial reading of the text. Hagar and Ishmael were finally ejected from the believing community not because they were not of the circumcised, for Ishmael in fact did receive the old covenant sign in his flesh (see Gen. 17:25). Instead, Hagar and Ishmael were rejected because they were not heirs of the promise to Abraham (21:10; Gal. 4:30).
Ultimately, Hagar likely had true faith in the one true, creator God (Gen. 16:13), though it is difficult to be sure. It is more probable that Ishmael lacked faith given his persecution of Isaac, which Paul mentions in Galatians 4:29. He is apparently referring to Genesis 21:9, wherein it is written that Sarah saw Ishmael laughing — the word translated as “laughing” often has sinister overtones in Hebrew. Ishmael, it seems, mocked Isaac, the son of promise.
Such harassment, Paul writes, is the typical response of our Father’s enemies to His children (Gal. 4:29). The Judaizers in Galatia, who by their confidence in their own works revealed the darkness of their hearts, did not disturb and harass the Galatian Christians outrightly. Yet the trouble these false teachers introduced into the Galatian churches was persecution in kind, if not in degree. This trouble, however, could not last forever given the freedom of grace in the biblical gospel. Confident that the Galatians would stand firm in their freedom, Paul knew these troublers would be cast out of the church (vv. 30–31). Today we may be confident, John Calvin says, that “to whatever extent” false brethren “may harass us for a time, the inheritance will surely be ours.”