One of the great difficulties for the Jews in accepting The Lord Jesus as their Messiah was that he seemed to openly break the laws of Moses.  St. Matthew provides the words of Jesus himself on this matter, in the course of the Sermon on the Mount.  St. Jerome (d. 430), the greatest of western biblical scholars, adds his elucidations to the words of The Lord in his commentary on the Gospel of St. Matthew:

" 'Do not think that I have come to abolish the law or the prophets.  I have come not to abolish, but to fulfill.'  He said this either because he fulfilled what was prophesied of him by others, or because he fulfilled the law, which before was rude and imperfect on account of the weakness of the law's hearers, by his preaching on doing away with anger, dispensing with the law of retaliation, and on the lust hidden in the mind.  

" 'Until heaven and earth pass away.'  We are promised a new heaven and a new earth, which would be made by God.  If the new heaven and earth are to be created, the old heaven and earth must pass away.  

" 'Neither a single iota nor a single apex shall depart from the law until all [the law] is fulfilled.'  This figure of speech shows that even that which is considered least in the law is full of spiritual mysteries, and that everything in the law is recapitulated in the Gospel."

The "iota" is the smallest of Greek letters, corresponding with the English letter "i"; the "apex" is merely the tip of a Greek letter.  

St. Jerome refers to an important element in the understanding of the Scriptures, when he speaks of the "recapitulation" of the old law in the new.  This recapitulation shows how the old law is fulfilled by the new: the Apostles, in their gospels and epistles, show how the sacrificial lamb of Isaiah is the Lamb of God, how Christ is the new Adam, how the old sacrifices of the temple are figures for the new Sacrifice which truly forgives sins, and so on.  Indeed, there was a saying among the Fathers of the Church that, "The New Testament is hidden in the Old, and the Old Testament is unveiled by the New."