This is why Paul attacks the law, when it is in the mouths of those who would commend themselves. This is why he glories in the law when it is in the mouth of the one who loves. This is why Jeremiah attacked the Temple, and why Solomon built it. This is why God commanded sacrifices, and then told the people He actually wanted mercy instead. This is why ministers baptize the repentant and then laugh at the baptism of the unrepentant. This is why the Westminster Confession is one of the glories of Western civilization, which it is, as well as a set of blinkers for Calvinistic workhorses. This is why the saints of God have been called many different things — Catholics, Puritans, Methodists — and why they have frequently been persecuted by men bearing the name of yesterday’s godliness.
The worldly Bible teacher, in love with the flesh, wants everything to stay put. Sons of Sarah must always remain sons of Sarah. To say that sons of Sarah can somehow become sons of Hagar is to talk nonsense to him. He wants everything static so that he has a foolproof method for knowing what side he is on. But that is not how spiritual battles go. (Doug Wilson, http://www.dougwils.com/Galatians/The-Cruciform-Heart.html)
Or here…