Is justification by faith a new development in God's salvation plan? In answer to that, Paul argues how Scripture clearly reveals that justification by faith, far from being a new development, has always been God's way of saving mankind. He points to the account of Hagar and Ishmael and of Sarah and Isaac as evidence.
However, the Jerusalem that belongs to God is characterised by her free citizens (v. 26), who by faith are set free by Christ from bondage.
″If you had truly heard and understood the meaning of this story in the Pentateuch (often referred to as Torah or the Law),″ Paul says, ″How is it possible for any of you to want to be under the law?″ (see Galatians 4:21).
Out of Abraham came two sons: Ishmael by Hagar, who was a slave, and Isaac by Sarah, a free woman (v. 22). However, Ishmael was conceived through human effort (flesh) because Sarah thought of giving Abraham an heir through proxy, namely Hagar her handmaid. Isaac, however, was supernaturally conceived, the result of a divine promise, since Sarah had already passed her child-bearing age (v. 23). The sons represent two distinct lineages from Abraham.
But there are implications, Paul continues. The Judaizers claim that they are aligned with Isaac, when in fact they are not. Hagar represents the old covenant based on the law that was enacted at Mount Sinai (v. 24). Why? Because like her, the law-requiring human effort to keep-results in slaves as children, imprisoning all who come under it. Therefore, Paul argues, all who look to the law for salvation, including those presently in Jerusalem, are in bondage (v. 25). They are Hagar's children in the lineage of Ishmael.
However, the Jerusalem that belongs to God is characterised by her free citizens (v. 26), who by faith are set free by Christ from bondage. They are in the lineage of Isaac, the children of the promise and hence the children of Sarah. ″And that's who you are,″ Paul points out to the Galatians (see vv. 28, 31). So why would anyone want to adopt the law and end up aligning with Ishmael?
The right thing to do, Paul notes, is to throw this heretical teaching out, just like God told Abraham to obey Sarah's request to ″get rid″ of Hagar and Ishmael (v. 30; see Genesis 21:10-12). Salvation will never come through the work of the flesh (as represented by Ishmael). And if it is allowed to stay, Paul warns, it will cause great harm as is happening now (v. 29).
Attacks on our faith happen frequently. The way to overcome them is to hear what God is saying through Scripture: it is through faith in Christ alone that one becomes a free child of Sarah.