This question is about the Law of God, which is pretty controversial among the people.
In Matthew 5:17-20, Jesus states that He has come to fulfill the teachings of the Law of Moses (the Torah) and the prophets. He also states that “not the least point of the Law will be done away, not until the end of all things. So then, whoever disobeys the Law and teaches others to do the same, will be least in the Kingdom of heaven (Matt 5:18-19, Good News Bible version). There are some things which Jesus said that contradict to the statement He mentioned above. In Matt 15:1-20, He says that it is not what goes into the mouth of a person that makes him unclean ritually, but rather what comes out of it makes him unclean. I understand this verse and he means to say that it doesn’t matter what we eat. But this contradicts His statement that is mentioned above because there are certain animals that are unclean to be eaten according to the Law of Moses (Leviticus). The above statement also contradicts to Apostle Paul’s teachings that we don’t have to be circumcised and that it doesn’t matter what we eat, and that the Gentiles (non-Jews) don’t have to follow the Law of Moses to be Christian. So, how can these contradictions be cleared?
You need some context to interpret Matthew 5:18-19 and to apply it to such situations as Matthew 15:1-20. In the Torah we are told that “You must obey my laws and be careful to follow my decrees. I am the Lord your God. Keep my decrees and laws, for the man who obeys them will live by them. I am the Lord (Leviticus 18:4-5). There are two ways to righteousness as described by Jesus (and by Paul in Romans ch 3-6). One way to righteousness is by fully keeping the Law. The problem with this approach is that no one could fully obey all of the Law. We are sinners. The way Paul put it, “through the commandment (ie the Law of Moses) sin became utterly sinful.” (Romans 7:13). When Jesus tells us that whoever disobeys the Law (of Moses), they are the least in the Kingdom of heaven, he is talking about seeking righteousness through law-keeping, which we all know is impossible.
Jesus came to fulfill the Law (Matthew 5:17). This is true in multiple ways. He fulfilled the Law by being the only adult human being to actually fully obey it. He also fulfilled it by taking the penalty due to those who do not obey the Law. He also fulfilled the Law in that his life and death fulfilled the requirements of the Law so that we do not have to fully obey it in order to be saved. In other words, he provided an alternative path to righteousness, through faith in his blood and his sacrifice to fulfill what we could never do on our own. This is the context of the comments made by Jesus about the Law of Moses. In Matthew 15:1-20 he is definitely not contradicting himself. First of all, Jesus was a Jew and he obeyed the letter of the Law of Moses perfectly. He did not eat unclean meat. Yet, he died so that the rest of us no longer have to meet the law that he met! Because he fulfilled the Law in this sense, we, as Christians, are no longer under this law, and are under grace. We are no longer required to obey the Law of Moses which prohibited the eating of certain kinds of meat. For us (unlike those seeking righteousness by obeying the Law of Moses), all food is truly clean. This is not a contradiction. It is true that male Jewish children had to be circumcised, not according to the Law of Moses, by the way, but according to the covenant given to Abraham. But Paul made it clear that for those who are baptized into Christ, we have died to this kind of law and are now under grace. For us circumcision is not needed, as our righteousness is found, not in Law but in Christ. This is shown in Colossians 2:9-23. We who are saved by Christ have found a new means to righteousness, and it is through faith in Jesus Christ, not through Law-keeping. Thanks to God.