Jesus said, "You are the salt of the earth; but if salt has lost its taste, how can its saltiness be restored? It is no longer good for anything, but is thrown out and trampled under foot.
"You are the light of the world. A city built on a hill cannot be hid. No one after lighting a lamp puts it under the bushel basket, but on the lampstand, and it gives light to all in the house. In the same way, let your light shine before others, so that they may see your good works and give glory to your Father in heaven.
"Do not think that I have come to abolish the law or the prophets; I have come not to abolish but to fulfill. For truly I tell you, until heaven and earth pass away, not one letter, not one stroke of a letter, will pass from the law until all is accomplished. Therefore, whoever breaks one of the least of these commandments, and teaches others to do the same, will be called least in the kingdom of heaven; but whoever does them and teaches them will be called great in the kingdom of heaven. For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven."
The only way you can actually be a Bible believing Christian is if you are capable of believing two or more, completely contradictory, statements to be equally true. As someone who is prone to such self-delusional thinking would be regarded as a suitable case for treatment if their magical thinking concerned anything other than religion, I think it is fair to say that holding everything in the Bible to be equally true is not a logical or reasonable position to take.
You might think that there would be more contradictions in the Old Testament but this is not necessarily the case. There are some massive contradictions in the text of the New Testament as well. Even the four gospels differ from each other, sometimes to a very large extent. For example the timeline of Christ's ministry in the Gospel of John is radically different to the timelines in the other three gospels. John reports incidents happening near the start of his ministry that the other evangelists insist happen towards the end of his ministry. I doubt that this is because one or more of the gospel writers set out to lie because I don't think they set out to provide an exact and accurate historical record of the life of Jesus. I think they set out to bring together the various stories about Jesus Christ that had been passed down the years by world of mouth between the crucifixion of Christ and the writing of the gospels. It is possible that could have been a hundred years or so. At the very least it would have been forty or so years. Also, I very much doubt that it would have ever crossed the minds of any of the evangelists that they were writing down the words of God. That would have been considered about the worst blasphemy possible for people who thought even saying the name of God was a presumption too far. Therefore, believing everything in the Bible to be the word of God and, therefore, beyond contradiction, is not only logically impossible to do it is also blasphemous and against the spirit in which the Bible was written in the first place. Bible believing Christianity is a post-Reformation invention to provide comfort and a sense of superiority to those followers of Jesus Christ who were unable, are unable, to live with the freedom that comes with being justified by Christ.
It is this freedom, a freedom from legalism and the oppression that accompanies it, that is second place only to the proclamation of the resurrection of Christ, in the theology of Saint Paul. I find it incredibly ironic that many of those within the Christian church who lionize Paul, sometimes to the point of seemingly making Jesus subservient to his foremost evangelist, and regard Saint Paul's concept of justification by faith as being the very gospel itself, ignore the much better news that Paul wants to tell us, that, as disciples of Jesus Christ, we are no longer subject to the law. There is no ambiguity in Paul's teaching on this matter. He boldly states that righteousness is found in being in Christ and not in following rules and regulations. Paul tells his listeners that they can forget all about the laws in the Old Testament, including those laws that were very important to the Jews, such as circumcision and dietary restrictions. But modern day Bible worshipping, Saint Paul worshipping Christians do not want to let go of the law. They love the law. It gives them power and certainty although, unfortunately, both for them and for the rest of us, it is completely the wrong sort of power and certainty. It is the power and certainty that comes from being bound to human law not the power and certainty that comes with being a branch that has been grafted on to the vine that is the Word made flesh and Son of God, looking only to him for spiritual and moral guidance.
Paul is no libertine. Although he is insistent that those who believe in Jesus Christ are not subject to the Law he is also insistent that this doesn't mean that they can behave in any way they might want to. Paul expects those who believe in Jesus Christ to behave in the way they should want to as children of God who share in the mind, in the desires and motivations, of the Son of God, Jesus Christ. For Christians moral behaviour should be a natural, instinctive thing not something imposed on them by statutes and with the threat of punishment for non-compliance. Christians are the salt of the earth and the light of the world. As Jesus points out in today's gospel reading they are expected to behave as such because otherwise what use are they? They are no use whatsoever.
Both Jesus and Paul are convinced that the Law was not a mistake. For the two of them it was a gift from God which, when adhered to, kept the people of God in a covenantal relationship with God, until the time that God entered into a new and final covenant with his people. Both Jesus and Paul believed that this new covenant was signed by God when he raised Jesus from the grave and in doing so made the promise that all people could share in eternal life. This is why Jesus sates that he has come to fulfill the Law. The Law was never complete in itself. It was never the final destination. It was, like the words of the prophets, a pointer towards that which was to come, namely the Messiah, the Word made flesh, the Son of God, Jesus Christ.
So Jesus did not come to abolish the Law or even to replace it. His relationship to the Law was like that of the butterfly to the caterpillar. The children of God who were made subject to the Law of God in Old Testament times were spiritually and morally, exactly that, children. But the brothers and sisters of the Son of God and Son of humanity are expected to have become adults with an adult capability of choosing their own manner of life. The Law was their childhood home, it kept them safe whilst they grew up. But now they have grown up and have made their own decision to follow Christ it is time for them to leave the home of their youth and strike out independently.
A person who is an adult in the faith of Christ should know how to behave without being told what he or she can and cannot do in every situation. Jesus gave us the key to achieving this ideal when he took that part of the old Law that was not about practicalities but about attitude. Jesus tells us that we should love God and love everybody. He gives us a few major examples of how this should play out in our lives such as the necessity of caring for the poor and the outcast. But he does not tell us exactly how we should do this in detail. He refuses to prescribe our actions. Such was the way of the Law. But the Law has been fulfilled and the new way is one of personal responsibility based on the commandment to love.
I think this is what Jesus is referring to when he says he has come to fulfill the Law and the prophets. I think he says that not one letter, not one stroke of a letter, will pass from the law until heaven and earth pass away, because he is not abandoning or denying the Law. The Law has not died it has pupated and out of the chrysalis of Christ has been born something that is from the Law but of a new nature. The word of the Law has left the statute books and become enfleshed in the followers of Christ. The Law has been raised from the dead and has become a living thing.
Of course, I may well be wrong. It may be that this passage from the Gospel of Matthew is another example of the Bible contradicting itself. The bit about the Law not passing away may have not been said by Jesus, who certainly acted in ways that showed that his interpretation of the strictures of the Law was a lot more imaginative and fluid than that of the Pharisees, for example. Perhaps it was inserted to help sell the gospel to orthodox Jews. Perhaps it was inserted by a proto-Puritan who wanted, like so many do today, to bring back the Law and rid Christianity of that pesky freedom that makes telling people what to do and think so difficult.
Whatever, it does not matter. We have the example of Christ to be our guide which is something that is above all else. Christ showed us a new way of living, a new way of living for eternity; forever free to love as Christ loves us. To turn our back on this freedom and demand subjection to the Law as if Christ did not fulfill the prophets and did not free us from the chains that bound us, is to turn our backs on Christ and his Father in heaven. And that would be a very childish and contradictory thing to do.