Fulfillment of the Law

Gospel Reflection for Wednesday June 11, 2025, Memorial of St. Barnabas, Apostle

Sermon on the Mount

“Jesus said to his disciples: “Do not think that I have come to abolish the law or the prophets.
I have come not to abolish but to fulfill.” Matthew 5:17.

In today’s Gospel, we have a well-known passage in which Our Lord affirms to the listeners of the Sermon on the Mount that He has not come to get rid of the Law and the Prophets, but, instead, He has come to fulfill them. Far from being a break with what came before Him, Christ tells the people that the Beatitudes and other teachings from the Sermon are there to complete the law given under Moses. Thus, we see a preparatory nature to the Old Testament. The Law is given to the people, not as the final form of revelation, but as a way to prepare the people to receive the Incarnate Lord.

To this end, St. Thomas Aquinas gives five ways Our Lord fulfills the law and the prophets in his commentary on the Gospel of Matthew. I want to briefly look at each of these ways:

“First, because those things that were prefigured in the law and the prophets concerning Christ, he fulfilled in his actions: what is written must be fulfilled in me (Luke 22:37).”¹

St. Thomas begins with the prefiguring of those Old Testament figures who had prepared the way for Our Lord. We can look at the figures of Adam, Moses, King David, etc., and see how their actions are imperfect foreshadowings of what Our Lord would do. For example, we can see the uniting of the Tribes of Israel, at least for a time, under the rule of King David. This temporary unity prefigures the perfect unity under the Eternal King. Further, in Our Lord we find the fulfillment of all prophecies found in the Old Testament. For example, we can look at Isaiah 7:14:

“Therefore, the Lord Himself will give you a sign. Behold, a virgin shall conceive and bear a son and shall call His name Immanuel.” Isaiah 7:14

The prophet foretells the coming of the Messiah, conceived and born of a virgin, who will truly be God with us. This is fulfilled in Jesus Christ as affirmed by St. Matthew:

“All this took place to fulfill what the Lord had spoken by the prophet: ‘Behold, a virgin shall conceive and bear a son, and His name shall be called Emmanuel’ (which means, God with us).” Matthew 1:22-23.

Every Old Testament prophecy is perfectly fulfilled in Jesus Christ. If they were not fulfilled, He would not be the Messiah.

“Second, by observing the legal requirements to the letter, when the fullness of time had come, God sent his son (Gal 4:4).²

This second way emphasizes the historical reality of the coming of Christ. Quoting St. Paul and his letter to the Galatians, St. Thomas cites that Christ was born in the fullness of time. This specific time, ordained by the providence of God, was the most perfect time for the redemption of the world to happen. It is the apex of history where we see the convergence of the Jewish faith, Roman rule, and Greek wisdom. This serves as the fullness of time and makes man prepared by God to receive the Incarnate Word.

More than that, God sent His son born under the law.³ From the time of His birth, Our Lord fulfilled the precepts of the Law to their perfection. We see this in the Gospels from the very beginning, “And when the time came for their purification according to the Law of Moses, they brought Him up to Jerusalem to present Him to the Lord (as it is written in the law of the Lord, ‘Every male that opens the womb shall be called holy to the Lord’) and to offer a sacrifice according to what is said in the law of the Lord, ‘a pair of turtledoves, or two young pigeons.’”⁴ At the very beginning of His life, His parents brought Him to the temple to be dedicated to the Lord. Not because the Incarnate Second Person of the Trinity needed to be dedicated to the Lord, but because He was born under the law, and thus they fulfilled the mandates of the Law. Even Mary, who needed no purification, since she did not suffer any rupture in giving birth to the Lord, underwent the required purification of a woman who gave birth, according to the law.

“Third, by working through grace, which the law of nature could not do: for every law is for the sake of making us just men, but Christ did this by the Holy Spirit: for what the law could not do, God has done by sending his own Son (Rom 8:3).”⁵

The Law of Moses, of itself, is not salvific.⁶ Because of this, the grace of Jesus Christ, poured out from the cross, is necessary for salvation. St. Thomas refers to the Law of Moses as the Law of Nature, precisely because it can cause a man to act in a just way, but observance of the Law does not make a man justified. This, alone, can be done by the Law of Grace, that is, Sanctifying Grace being infused into the soul of the person and transforming them. Not merely made to appear justified, but actually being made to be justified.

“Fourth, according to Augustine, by satisfying for the sins by which we were made transgressors of the law; hence, having borne the transgression, he is said to have fulfilled the law: whom God proposed to be a propitiation (Rom 3:29).”⁷

From the very beginning, man transgressed the law.⁸ This put man in a state of radical contradiction to God. We lost our state of Grace and were made enemies of God. For this reason, God sent His Son in order to redeem man and to return us to friendship with Him. This fourth way is an extension of the third way above. St. Thomas cites the death of the Lord, which was prophesied and willed by God from the very beginning.⁹ The Son is sent to redeem mankind through His blood. In essence, the sacrifice of Christ, which is an act of perfect Charity, is more pleasing to the Father than the whole of man’s sin is displeasing to Him. Thus, man is redeemed.

“Fifth, by applying certain perfections to the law which were either for the understanding of the law or for the greater perfection of justice, for the law brought nothing to perfection (Heb 7:19); and these things seem to be the intention of Christ, since, when he made mention of all legal restrictions, he added be you therefore perfect (Matt 5:48).”¹⁰

Finally, the Law of Moses was not perfecting in itself. It merely allowed those who followed it to be morally prepared to receive the perfection of Grace. By no means does this mean that following the Ten Commandments is futile. By no means! But they are not the end-all be-all of the Law. Truly, they are the minimum that we must do. They are the minimum of what we must do to attain eternal life. They are the avoid evil half of morality. But we also must do the good. We must be perfected in charity to be united to God.

Be perfect is the command that only Christ can give us. Look no further than Our Lord’s words on Marriage in the Gospel of Matthew. The Pharisees asked Him about the allowance for divorce. Our Lord replies that Moses allowed divorce because of the hardness of hearts.¹¹ But Christ calls us to more. How can He do this? Because He gives the grace for perfection. He elevates marriage from an institution to a sacrament and through it, offers grace to be perfect. Thus, divorce is not permitted. Christ offers the necessary divine aid to fulfill the marriage covenant.

Simply, the Law commands love your neighbor as yourself.

Christ commands love one another as I have loved you.

Christ fulfills the law in order to make us perfect.

1. St. Thomas Aquinas, Commentary on the Gospel of Matthew, C. 5, L. 6, 469.

2. Ibid.

3. Galatians 4:4.

4. Luke 2:22-24.

5. Commentary on Matthew, 469.

6. See Romans 3:28, Galatians 2:16 and 3:11, The Council of Trent, Decree of Justification, and CCC 1963-1964.

7. Commentary on Matthew, 469.

8. Cf. Genesis 3.

9. Cf. Genesis 3:15.

10. Commentary on Matthew, 469.

11. Cf. Matthew 19:8.