Jesus did not abolish the law or the prophets
‘Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfil them. For truly I tell you, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. Therefore anyone who sets aside one of the least of these commands and teaches others accordingly will be called least in the kingdom of heaven, but whoever practises and teaches these commands will be called great in the kingdom of heaven. For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven. (Mat 5:17-20)
This disclaimer is necessary because the teaching that follows, prohibiting ‘legal’ wrongdoing in response to illegal wrongdoing, appears, according to the wisdom of this world, to be condoning the first wrongdoing.
To properly interpret the disclaimer requires an analysis of the teaching that follows, and the use of other sources identifying the aspects of the law and the prophets that he is upholding and perfecting on the one hand, and to identify the aspects that he is excising on the other.
Later in the Sermon on the Mount Jesus identifies what he means by the law and the prophets:
So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets. (Mat 7:12)
Later in his gospel Matthew provides a similar summary of the law and the prophets:
Hearing that Jesus had silenced the Sadducees, the Pharisees got together. One of them, an expert in the law, tested him with this question: ‘Teacher, which is the greatest commandment in the Law?’
Jesus replied: ‘“Love the Lord your God with all your heart and with all your soul and with all your mind.” This is the first and greatest commandment. And the second is like it: “Love your neighbour as yourself.” All the Law and the Prophets hang on these two commandments.’ (Mat 22:34-40)
As we shall see below, the teaching does not change what constitutes original wrongdoing. In fact, as Jesus argues, his law is stricter and deeper against wrongdoing, both original and responsive. Jesus does not teach that murder, assault, adultery, stealing etc. are justified or right. However, the lawful responses to such wrongdoing are subject to radical change.
The teaching on fulfilment and accomplishment are also important. The word translated ‘fulfil’ means fill up a deficiency, to make full, to perfect, to set forth fully. Jesus came to perfect the law, to fully develop it into a mature body, to remove its last impediment to perfection: its regulation and sanction of wrongdoing in response to wrongdoing. This can be seen in the other teaching on this topic from Paul:
Let no debt remain outstanding, except the continuing debt to love one another, for whoever loves others has fulfilled the law. The commandments, ‘You shall not commit adultery,’ ‘You shall not murder,’ ‘You shall not steal,’ ‘You shall not covet,’ and whatever other command there may be, are summed up in this one command: ‘Love your neighbour as yourself.’ Love does no harm to a neighbour. Therefore love is the fulfilment of the law. (Rom 13:8-10)Paul’s message is this: debts should be paid, and doing so ends the obligation to pay. But the obligation to love does not end and it remains regardless of whether the other person is a debtor or a creditor. The duty to refrain from doing harms to your neighbour applies even if his debt to you is valid, overdue and unpaid. The perfect law provides no allowance of harms as a means of recovering debts.