21 Tell me, you who desire to be under the law, do you not listen to the law? 22-23 For it is written that Abraham had two sons, one by a slave woman and one by a free woman. But the son of the slave was born according to the flesh, while the son of the free woman was born through promise. 24 Now this may be interpreted allegorically: these women are two covenants. One is from Mount Sinai, bearing children for slavery; she is Hagar.

25-26 Now Hagar is Mount Sinai in Arabia; she corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above is free, and she is our mother. 27 For it is written, “Rejoice, O barren one who does not bear; break forth and cry aloud, you who are not in labour! For the children of the desolate one will be more than those of the one who has a husband.”

28-29 Now you, brothers, like Isaac, are children of promise. But just as at that time he who was born according to the flesh persecuted him who was born according to the Spirit, so also it is now. 30 But what does the Scripture say? “Cast out the slave woman and her son, for the son of the slave woman shall not inherit with the son of the free woman.” 31 So, brothers, we are not children of the slave but of the free woman. Galatians 4:21-31 English Standard Version

The Christians in the region of Galatia had been led astray by people who insisted that they could only be saved if they strictly followed all the laws that were taught in the Old Testament. What was Paul's important challenge to that sort of thinking? (vs 21)

He asks them if they have taken time to really consider all that is actually taught in the Law. There's always a danger when it comes to people who make 'rules for Christians to live by', that they have been selective in what they say the Bible teaches! That’s true of every cult. On the other hand, Paul had been a Pharisee (the strictest party of the Jewish religion) before he was converted to Christ, so he was well qualified to use the illustration he gives in vs 24.

The illustration goes back to the Old Testament book of Genesis. In Chapter 16, we read of how Abram's wife, who was childless, arranged for him to take her servant maid, Hagar, as a wife, so that she could have children through her. Hagar was an Egyptian, and Mount Sinai was where God had given Moses the Ten Commandments. Hagar did indeed bear a son to Abram, called Ishmael, but he was not the child God had promised Abram and Sarai through whom descendents as many as the stars of heaven would come. Paul then quotes some words from the prophet Isaiah which told how the descendents of the one who’d been barren would eventually be more numerous than those who came from the wife who had conceived.

Who was the son God promised, and what happened between him and Ishmael? (vs 28-29)

It seems that when Isaac was eventually born, the older son, Ishmael, had laughed – probably in a taunting or mocking way. It upset Sarai deeply and she told Abram to send Hagar and Ishmael away. Abram did so, reluctantly, and only after God told Abram that He would take care of Ishmael, and build up a nation from him. All of this is part of Israel's history, but Paul used it as a picture for the Galatians to help them to see that they were not to be under the slavery of the Law - but to live in the liberty of God's promise.

In the first verse of the next chapter of this book Paul makes the application from this. He says to the Galatians: “For freedom Christ has set us free; stand firm therefore, and do not submit again to a yoke of slavery.” That's something we must keep in mind whenever we are confronted by people from sects and cults who try and bring us back into a legalistic system of obeying their man made rules! To turn back to a list of such rules is to trample upon the blood Christ shed in order to make us truly free.