-- Mt 5:17-19
Jesus, Israel's Messiah and therefore the greatest in the kingdom of heaven, was to fulfill the Law by keeping it in its all embracing detail - according to his own words, down to "the least of these commandments". He is in fact the only one who could keep it perfectly. On their own admission the Jews were never able to observe the Law in its entirety without violating the least of its precepts. This is why every year on the Day of Atonement the children of Israel ask God's forgiveness for their transgressions of the Law. The Law indeed makes up one inseparable whole, and St. James recalls, "Whoever keeps the whole law but fails in one point has become guilty of all of it."
-- CCC 578