Ben-Paul was not preaching replacement theology. He was speaking to the Galatans, who where gentile believers who were attempting to follow “Judaized” Christian beliefs at the expense of the Christianity that Paul taught. Paul was making the argument not that Christianity had replaced the Jews, but that the Christian belief of salvation through grace was superior to salvation through following the Law. Below, I’ve cut and pasted from a commentary on Galatians for anyone who is interested:
Title : Life Application Bible Commentary: Galatians
Edition : First
Copyright : Copyright © 1994 by The Livingstone Corporation. Tyndale House Publishers, Inc. Wheaton, Illinois.
Under the influence of the false teachers (the Judaizers), the Galatians wanted to submit to the Jewish law. Paul, completely “perplexed” by this (4:20), wanted to turn them back to accepting salvation by grace alone. He confronted them directly by saying, “Do you really know what the law says? You want so badly to submit to it, yet do you even understand it?” The Galatian believers, most of them not from a Jewish background and thus with little more than an elementary understanding of the Jewish law, may have answered an indignant yes. Hopefully they would have halted long enough to realize the impossible standards under which they were placing themselves. Galatians 4:22 For it is written that Abraham had two sons, one by a slave woman and the other by a free woman. (nrsv) Paul turned to an argument from the Jewish Scripture and the life of Abraham. The Law, the Torah, included all the books of the Pentateuch, Genesis through Deuteronomy. While the Judaizers focused on the minute aspects of law keeping described in Leviticus and Deuteronomy, Paul turned to another part of the Law, the historical account of Abraham, father of the Jewish nation (see also 3:6-29), to illustrate his point. The Judaizers, indeed all Jews, took great pride in their descent from godly Abraham. However, as John the Baptist and Jesus pointed out, merely being descended from Abraham was not enough to secure salvation (see Matthew 3:9; John 8:37-44). Paul made the same point in this section, though from a slightly different angle. The story, originally recorded in Genesis 16 and 21:1-21, was summarized by Paul as a fundamental spiritual lesson demonstrated by Abraham, his two sons, and his two wives. Abraham had more than two sons, but Isaac and Ishmael were his first two and are the ones important to this illustration. In ancient times, a mother’s status affected the status of her children. Paul reminded his readers that Abraham had two types of sons—one born of a slave woman and one born of a free woman. Paul wanted the Galatians to consider which type of descendant these Judaizers were more like and then decide which they themselves desired to be like.