Galatians 4:28 Now we, brethren, as Isaac was, are the children of promise.
29 But as then he that was born after the flesh persecuted him that was born after the Spirit, even so it is now.
30 Nevertheless what saith the scripture? Cast out the bondwoman and her son: for the son of the bondwoman shall not be heir with the son of the freewoman.
31 So then, brethren, we are not children of the bondwoman, but of the free.
Here we see that just as Isaac inherited the promises made to Abraham, so also are believers the recipients of God’s redemptive promises , because they are spiritual heirs of Abraham. It goes own to tell of how Ishmael mocked Isaac which helps us to see that there will always be conflict between believers an unbelievers. Paul is warning them here that there will never be peace between the flesh and the Spirit. Then we are told to cast away that which is of the law and embrace the freedom that comes with righteousness. Christians are not of the flesh, but are of the Spirit. We are righteous, with faithful Abraham, because we have faith in the Lord Jesus Christ. We are to follow the truth of the word of God and not be legalistic in trying get closer to God. This chapter has helped us to see that we need to stay in the word of God to know that we are following in His righteousness and not listening to false doctrines.