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."
"In order that the Scripture might be fulfilled" (Jn 19,28)
“I have come not to abolish the law, but to fulfill it”... Indeed, at that time, by his own power and in his own person, the Lord fulfilled all the mysteries the law foretold concerning himself. All prophecies were fulfilled by his passion. When, as holy David predicted, a sponge full of vinegar was offered him on the cross, he accepted it and said: “It is fulfilled”; and bowing his head, he gave up his spirit (Jn 19,30).
Now as well as carrying out himself all that had been prophesied, he also gave us commandments to carry out. Of old the easier commandments laid down by the law (Ac 15,10) were not observed, but we, by grace and the power of the cross, are expected to observe more difficult ones.