For the Wednesday of the Third Week of Lent, we hear St. Matthew’s account of Our Lord speaking about the Law and its fulfillment:
“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. Amen, I say to you, until heaven and earth pass away, not the smallest letter or the smallest part of a letter will pass from the law, until all things have taken place. Therefore, whoever breaks one of the least of these commandments and teaches others to do so will be called least in the Kingdom of heaven. But whoever obeys and teaches these commandments will be called greatest in the Kingdom of heaven.’” Matthew 5:17-19.
This comment by Our Lord is very important in the context in which we find it. It is given in the midst of the Sermon on the Mount, after He gives to the people the Beatitudes. It is fitting that this affirmation of fulfillment be given after what might appear to be a replacement law given in the Beatitudes. Our Lord affirms that He has not come to abolish but to fulfill.
The Greek word used is πληρωσαι (plērŏō). This word means to make complete. This is the context in which we have to see the Beatitudes and the entire Sermon on the Mount. Our Lord is not replacing anything. He is completing what had been given at Sinai and bringing it to its salvific end. He is not replacing the teachings of the prophets; His actions are the completion of what had been prophesied by them. This means that the New Testament both includes and completes what was given in the Old Testament.
This is why the Catholic Church, with all of its rituals and moral teachings, is so important. In particular, the sacramental system completes what was given under the Mosaic Law. No longer are we circumcised in the flesh, but we are circumcised in spirit through the waters of Baptism. No longer do we make public confession before the sacrifice in the temple, but we confess to the priest acting in persona Christi in the confessional. No longer is marriage liable for divorce, but it is returned to the beginning, and what God has brought together, no man can put asunder.1
Most importantly, no longer do we sacrifice many lambs and consume their flesh as a redemptive sacrifice; we now participate in the one sacrifice of the Lamb of God and consume His flesh and blood so that we might have life in us through the Eucharist.2
In these sacraments, as well as the others, the Mosaic Law is not abolished; it is fulfilled. Just like with the Moral Law, Christ did not throw out the Ten Commandments; He affirms them and gives us the Beatitudes so that we do not just avoid sin, but we seek virtue. Likewise, in the sacramental system, Christ takes the Old Testament practice and perfects it. Where the Sacraments of the Old Law are solely in the flesh, the Sacraments of the New Law are efficacious for the soul.3
Christ took the entire Old Testament and made it complete. He did not throw out what had come before. He did not replace it with something completely new. He took what was given as a preparatory revelation and made it perfect in Himself. Only in the Catholic Faith does one find the perfect fulfillment of the Old Testament. Only in the Catholic Faith does one find how Christ made the Old Covenant complete. These are the commandments and the practices that make one great in the Kingdom of Heaven, as He tells us in the Gospel for today. We must hold fast to what He has handed down through the Apostles and their successors so that we may be found worthy to inherit the Kingdom of Heaven.
For more from Dr. McGovern, visit his Substack at A Thomist, Dedicated to the Theological tradition of St. Thomas Aquinas. Exploring Thomas’ Spiritual Theology and topics in Christology and Mariology.
Cf. Matthew 19:6.
Cf. John 6:53.
St. Thomas Aquinas, Summa Theologiae IIIa q. 62, aa. 1, 6.



I appreciate your explanations.
Great article and good examples of completion by the Lord and His Church. God bless you