Thomas Aquinas Commentary Galatians 4:28-31

"Now we, brethren, as Isaac was, are children of promise. But as then he that was born after the flesh persecuted him [that was born] after the Spirit, so also it is now. Howbeit what saith the scripture? Cast out the handmaid and her son: for the son of the handmaid shall not inherit with the son of the freewoman. Wherefore, brethren, we are not children of a handmaid, but of the freewoman." — Galatians 4:28-31 (ASV)

Having revealed the mystery concerning the mothers, he now reveals it concerning the sons.

He first distinguishes between the sons, and second, he states the main conclusion (verse 31). He distinguishes the sons on three counts:

1. Regarding their manner of origin.
2. Regarding their disposition and love (verse 29).
3. Regarding their right to the inheritance (verse 30).

The sons of Abraham are born in two ways. One is according to the flesh, like Ishmael, son of the bondwoman. The other is not according to the flesh, like Isaac, son of the free woman. This is not because Isaac was not born naturally, but because, as was already said, it was beyond the natural power of the flesh for a son to be born to a barren, elderly woman.

These two sons represent two peoples: Ishmael represents the Jewish people, who descended from Abraham by carnal propagation, while Isaac represents the Gentile people, who descended from Abraham by imitating his faith. Therefore, he says that we, brothers—that is, the faithful, both Jew and Gentile—are, like Isaac, children of the promise made to Abraham: They that are the children of the promise are accounted for the seed (Genesis 21; Romans 9:8). Note, however, that the children of Abraham according to the flesh are, literally, the Jewish people, but mystically, they are those who come to the faith for the sake of carnal and temporal goods.

Second, they are distinguished by their disposition, because the one who was born according to the flesh persecuted the one who was born according to the Spirit. This raises a difficulty, however, because it is not recorded that Ishmael persecuted Isaac, but only that they played together: When Sara had seen the son of Hagar, the Egyptian, playing with Isaac her son, she said to Abraham: Cast out this bondwoman and her son (Genesis 21:9).

I answer that the Apostle calls this playing a persecution because there is deception when an older person plays with a younger one, intending to deceive him. Alternatively, as some say, Ishmael compelled Isaac to worship the clay images he had fashioned. By this, he was teaching Isaac to turn from the worship of the one God. This was a significant persecution, since causing spiritual death is a greater evil than causing bodily death. Furthermore, Genesis calls it a game because Ishmael did this under the guise of a game.

Another difficulty arises: how did the children according to the flesh persecute, and how do they still persecute, the children according to the Spirit? The answer is that from the beginning of the early Church, the Jews persecuted Christians, as is clear in the Acts of the Apostles, and they would do the same even now if they were able.

In our own time, however, those who are carnal persecute spiritual people in the Church, even physically. These are the ones who seek glory and temporal gain in the Church. A gloss on this says, “All who seek earthly aggrandizement from the Lord in the Church belong to this Ishmael. They are the ones who oppose those making spiritual progress and who slander them. They have iniquity in their mouth, and craft and deceit on their tongues.” Furthermore, those who persecute the spiritual sons spiritually are the haughty and the hypocrites. For sometimes, those who are plainly carnal and evil recognize their guilt and humble themselves before the good, but the foolish persecute in others the goodness they themselves lack.

A further question arises from the fact that heretics whom we persecute claim that they are the ones born according to the Spirit and we are the ones born according to the flesh. I answer that there are two kinds of persecution. The good kind is that in which a person persecutes another to lead him back to good. This is what righteous men do to evil men, and spiritual men to carnal men, either to correct them if they are willing to be converted or, if they are obstinate, to destroy them, lest they contaminate the flock of the Lord. The other type of persecution is evil, that is, when a person persecutes another in order to pervert him; and this is what those born according to the flesh do to those born according to the Spirit.

Finally, regarding their right to the inheritance, they are distinguished by the authority of Scripture: Cast out the bondwoman and her son (Genesis 21:10). By this, we are given to understand that the Jews, the persecutors of the Christian religion, and carnal and evil Christians will all be cast out from the kingdom of heaven. As Scripture says, Many shall come from the east and the west and shall sit down with Abraham and Isaac and Jacob in the kingdom of heaven (Matthew 8:11), but Without are dogs and sorcerers (Revelation 22:15).

Furthermore, the bondwoman herself—that is, vice and sin—will be cast out: Every work that is corruptible shall fail in the end . The reason for all this is added: the son of the bondwoman shall not be an heir with the son of the free woman. In this world, the good are mixed with the wicked: As the lily among thorns, so is my love among the daughters (Song of Solomon 2:2). But in the eternal homeland, there will be only the good. It is said to Jephthah in Judges 11:2, You cannot inherit in the house of our father, because you are born of a harlot.

We obtain this freedom from Christ. Hence, the Apostle refers to the freedom with which Christ has made us free, and the Lord says, If therefore the son shall make you free, you shall be free indeed (John 8:36).