John Chrysostom

Here he states two objects and effects of the Incarnation, deliverance from evil and supply of good, things which none could compass but Christ. They are these; deliverance from the curse of the Law, and promotion to sonship. Fitly does he say, that we might "receive," "[be paid,]" implying that it was due; for the promise was of old time made for these objects to Abraham, as the Apostle has himself shown at great length. And how does it appear that we have become sons? …

Homily on Galatians 4 ↗

Theophylact of Ohrid

While we were young, we were subject to new moons and sabbaths, but when the appointed time of Christ's incarnation came, when the human race, having passed through every form of evil, needed healing, then "God sent His Son" (that is, He was pleased to come), "Who was born" (γενόμενον), He did not say: "through a woman," so as not to give justification to those who say that the Lord passed through the Virgin as through a channel, in a completely phantasmal way, but: "of a woman," that is, He received a body from Her very substance …

Commentary on Galatians ↗

Oecumenius

"But when the fullness of time had come," namely the time which it was necessary, he says, for Christ to come. For Daniel the prophet assigned the time of Christ's coming, which reached its accomplishment in the reign of Caesar Augustus, when also the incarnate economy of Christ began. (Dan. 9:24-27) "born of a woman." Therefore he did not say "by a woman," so that you would not suppose his coming to have been by way of the Mother of God [Θεοτόκου], but "of a woman," showing that from her the Lord took his body. …

Commentary on Galatians ↗

Ambrose of Milan

He says "his Son," not one of many, not "a Son" but his own. When he says "his own" he confirms that he has the property of eternal generation. This is the one whom he subsequently declares to have been born from a woman, so as to ascribe the fact of being born not to the Godhead but to the assumed body. He was made from a woman by assuming flesh and made under the law by observing the law. But that heavenly birth of his is prior to the law, while the incarnation happens later.

On The Faith 1.14 ↗

Jerome

But when the fullness of time had come, God sent forth his Son, born of a woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons. Pay close attention to the fact that it does not say 'made through a woman,' which the heresies of Marcion and others assert, pretending that Christ's flesh was imaginary. Rather, it says 'born of a woman,' so that he may be believed to have been born not just through her, but from her. …

Commentary on Galatians ↗

Thomas Aquinas

Here the Apostle applies to Christ the simile he has proposed. First, he makes the application; Secondly, he discloses the purpose of the reality that corresponds to the simile (v. 5). It should be noted that above, in the simile he proposed, there were four items pointed out in order, as has been said. But now, in applying them to Christ, he begins with the last, namely, the fixing of a time. The reason for this is that the time in which Christ was humiliated and in which the faithful were exalted turns out to be the same. …

Commentary on Galatians ↗