Galatians 4:28-31

²⁸Now you, brothers, like Isaac, are children of promise. ²⁹At that time the son born in the ordinary way persecuted the son born by the power of the Spirit. It is the same now. ³⁰But what does the Scripture say? ‘Get rid of the slave woman and her son, for the slave woman’s son will never share in the inheritance with the free woman’s son’ [Genesis 21:10]. ³¹Therefore, brothers, we are not children of the slave woman, but of the free woman.

Paul wraps up chapter 4 with a stunning visual. His allegorical viewing of Abraham’s situation reveals Ishmael persecuting Isaac. Ishmael did in fact persecute Isaac, apparently mocking him in some way (Genesis 21:9). But Paul says, “It is the same now” (v29). The Judaizers were persecuting the Galatians, just as Ishmael did Isaac. The Judaizers are the natural children of Hagar, not the children of promise. And the Galatians, along with all those who receive Christ by grace through faith, are the children of promise.

We can look at this at both a corporate and personal level. First and corporately, pagans persecute Christians; those of slave religions (everyone subscribes to a religion, for humans worship) persecute those of the free religion. They do so, because they have neither obtained nor understood the simplicity of the gospel (John 3:19-21). Second and personally, sin takes the law and condemns each of the children of God; legalism persecutes those who are free from the condemnation of the law. In both of these cases, a solution to the problem is needed.

Paul gives the solution by quoting Genesis 21:10, saying to get rid of the slave woman. On the personal level, we must get rid of the law’s condemnation that comes upon us due to our sin, for we can’t, due to sin, receive the inheritance by clinging to the law. We must not return to the law; it can’t save. The Galatians needed this advice; and we do as well, for we are neither slaves to sin, nor to the condemnation due us from the law (the curse), because we are Abraham’s offspring by faith in Christ, who bore the curse for us (Galatians 3:13). On the corporate level, we must realize as Christians that there is no unity available with the world apart from compromising the gospel, the pure doctrine of Scripture, and the authentic lifestyle of Christianity. Because Christianity is an intolerant (though non-violent) faith (Only One Way – Jesus Christ), there can be no agreement on essentials. One commentator says, “The reason why all ‘natural’ religious systems are bound to come into conflict with Christianity, the ‘supernatural’ system, is because they cannot co-exist as parallel paths to the same goal.” Therefore, corporately, Christianity must not compromise for the sake of unity with any false-gospel paganism, even if it comes calling under the name of “Christian” – such as, for example, Mormonism, Catholicism, or the JW’s. The Galatians must cast out the Judaizers; and we must cast out the false teachers among us.

Vincet Cheung concludes, "The way forward is to 'get rid of the slave woman and her son.' This seems to be Paul's indication that the Judaizers should be expelled from the community of the Galatians, along with their doctrines and practices. And this is also the way that we must treat all religious systems that would enslave us under adherence to Jewish rituals and customs, or inordinate reverence for Jewish culture and ancestry. Some forms of so-called 'Messianic Christianity,' for example, would subject Christians under such slavery again. Rather than expressing interest and obedience to these doctrines, the false teachers should be expelled from the church community. They do not introduce a superior version of the faith, but rather a slave religion, one that will not share in the inheritance," and we can respond in reverence and appreciation, not anxiety or envy (Psalm 37:1). Hebrews 12:22-24 is an apt conclusion, saying, "You have come to Mount Zion, to the heavnely Jerusalem, the city of the living God. You have come to thousands upon thousands of angels in joyful assembly, to the church of the firstborn, whose names are written in heaven. You have come to God, the judge of all men, to the spirits of righteous men made perfect, to Jesus the mediator of a new covenant."