“But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons.” Galatians 4:4-5
Martin Luther said, in his lectures on Galatians, concerning this whole Jesus being “born under the Law” concept:
But in what manner or way has Christ redeemed us? The manner was as follows: He was born under the Law. When Christ came, He found us all captive under guardians and trustees, that is, confined and constrained under the Law. What did He do? He Himself is Lord of the Law; therefore the Law has no jurisdiction over Him and cannot accuse Him, because He is the Son of God. He who was not under the Law subjected Himself voluntarily to the Law. The Law did everything to Him that it did to us. It accused us and terrified us. It subjected us to sin, death, and the wrath of God; and it condemned us with its judgment. And it had a right to do all this, for we have all sinned. But Christ “committed no sin, and no guile was found on His lips” (1 Peter 2:22). Therefore he owed nothing to the Law. And yet against Him – so holy, righteous, and blessed – the Law raged as much as it does against us accursed and condemned sinners, and even more fiercely. It accused Him of blasphemy and sedition; it found Him guilty in the sight of God of all the sins of the entire world; finally it so saddened and frightened Him that He sweat blood (Luke 22:44); and eventually it sentenced Him to death, even death on a cross (Phil. 2:8).
This was truly a remarkable duel, when the Law, a creature, came into conflict with the Creator, exceeding its very jurisdiction to vex the Son of God with the same tyranny with which it vexed us, the sons of wrath (Eph. 2:3). Because the Law has sinned so horribly and wickedly against its God, it is summoned to court and accused. Here Christ says: “Lady Law, you empress, you cruel and powerful tyrant over the whole human race, what did I commit that you accused, intimidated, and condemned Me in My innocence?” Here the Law, which once condemned and killed all men, has nothing with which to defend or cleanse itself. Therefore it is condemned and killed in turn, so that it loses its jurisdiction not only over Christ – whom it attacked and killed without any right anyway – but also over all who believe in Him. Here Christ says (Matt. 11:28): “Come to Me, all who labor under the yoke of the Law. I could never overcome the Law by My supreme authority, without any injury to Me; for I am the Lord of the Law, and therefore it has no jurisdiction over Me. But for the sake of you, who were under the Law, I assumed your flesh and subjected Myself to the Law. That is, beyond the call of duty I went down into the same imprisonment, tyranny, and slavery of the Law under which you were serving as captives. I permitted the Law to lord it over Me, its Lord, to terrify Me, to subject Me to sin, death, and the wrath of God – none of which it had any right to do. Therefore I have conquered the Law by a double claim: first, as the Son of God, the Lord of the Law; secondly, in your person, which is tantamount to your having conquered the Law yourselves.”
Paul speaks this way about this remarkable duel throughout his writings. To make the subject more joyful and clear, he usually portrays the Law by personification as some sort of powerful person who condemned and killed Christ. Christ then overcame death and conquered this person in turn, condemning and killing him. Thus in Eph 2:14-15: “He has slain the hostility in Himself” and again, in 4:8, on the basis of Ps. 68:17: “When He ascended on high, He led a host of captives.” He uses the same personification in the epistles to the Romans, the Corinthians, and the Colossians: “for sin He condemned sin” (Romans 8:3 [see also 2 Cor. 5:21, Col. 2:15]). By this victory of His, Christ has driven the Law to flight out of our conscience, so that it can no longer confound us in the sight of God or bring us to despair and condemn us. Of course, it does not cease manifesting our sin, accusing, and terrifying; but when the conscience takes hold of this word of the apostle – “Christ has redeemed us from the Law” – it is encouraged by faith and receives comfort. Then, with a kind of holy pride, it insults the Law and says: “I am not threatened by your terrors and threats at all, for you have crucified the Son and God, and crucified Him in a supreme act of injustice. Therefore the sin that you committed against Him is unforgivable. You have lost your jurisdiction, and finally you have been conquered and strangled not only for Christ but even for me as a believer in Him” He has granted us this victory. Therefore the Law has gone out of existence for us permanently, provided that we abide in Christ. Therefore “thanks be to God, who has give us the victory through our Lord Jesus Christ” (1 Cor. 15:57).
This also serves to support the idea that we are justified by faith alone. For when this duel between the Law and Christ was going on, no works or merits of ours intervened. Christ alone remains there; having put on our person, He serves the Law and in supreme innocence suffers all its tyranny. Therefore the Law is guilty of stealing, of sacrilege, and of the murder of the Son of God. It loses its rights and deserves to be damned. Wherever Christ is present or is at least named, it is forced to yield and to flee this name as the devil flees the cross. Therefore we believers are free of the Law through Christ who “triumphed over it in Him” (Col. 2:15). This glorious triumph, accomplished for us through Christ, is grasped not by works but by faith alone. Therefore faith alone justified. LW 26, 369-372