Jesus was not advocating the observance of the letter of the Law; he is inviting us and his hearers to realise the spirit of the Law, to come to the root of what the Law teaches.The quality of the Law comes from its fulfilment by Jesus. In Mt. 5:19 attention is focused on the teachers of the law - to teach by example. The Pharisees and doctors of the Law had relaxed and even nullified the Law of God as laid down by Moses - by their six hundred and thirteen man-made precepts which had taken precedence over the value of the human person. Eg. Honour thy father and mother (4th commandment) was forgotten in their zeal for the "sacredness" of the temple. A man could vow all his properties to the temple and be free of his obligation to his aged parents. So too a Sabbath took precedence over the human person in peril. eg. The parable of the good Samaritan.

The law therefore needs to be "perfected" and "fulfilled" and Jesus does this precisely through his own earthly ministry which in itself was a fulfilment of the Old Testament teachings.