Matthew 5:17-18 means that Jesus came the first time not to abolish the prophecies in the Mosaic law and the Old Testament prophets regarding the Christ's first coming, but to fulfill all those prophecies (Luke 24:44-48; e.g. Acts 3:22-26, Isaiah 53). Matthew 5:17-18 can't mean that Jesus came not to abolish the letter of the commandments of the Old Covenant Mosaic law, for he did come to do that,
You wrote all that stuff about what you think Paul is saying but if Paul is contradicting Christ, then its Paul that has the problem, not Christ.
Now you put part of this scripture up in what looks like an attempt to disprove what Jesus actually said, He also told us to we better keep the law better than the Pharisees, and told us to listen to the high priest..
Here is the scripture that you seem to be trying to disprove.
Jesus is making the letter of the law much more harder to keep and if we don't keep the harder version then we are in trouble. You seem to be saying that he is saying the opposite.
The Fulfillment of the Law
17Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them.
18For 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.
19Therefore 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 practices and teaches these commands will be called great in the kingdom of heaven.
20For 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.
Murder
21You have heard that it was said to the people long ago, You shall not murder,
a and anyone who murders will be subject to judgment.
22But I tell you that anyone who is angry with a brother or sister
bc will be subject to judgment. Again, anyone who says to a brother or sister, Raca,
d is answerable to the court. And anyone who says, You fool! will be in danger of the fire of hell.
23Therefore, if you are offering your gift at the altar and there remember that your brother or sister has something against you,
24leave your gift there in front of the altar. First go and be reconciled to them; then come and offer your gift.
25Settle matters quickly with your adversary who is taking you to court. Do it while you are still together on the way, or your adversary may hand you over to the judge, and the judge may hand you over to the officer, and you may be thrown into prison.
26Truly I tell you, you will not get out until you have paid the last penny.
Adultery
27You have heard that it was said, You shall not commit adultery.
e 28But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.
29If your right eye causes you to stumble, gouge it out and throw it away. It is better for you to lose one part of your body than for your whole body to be thrown into hell.
30And if your right hand causes you to stumble, cut it off and throw it away. It is better for you to lose one part of your body than for your whole body to go into hell.
Divorce
31It has been said, Anyone who divorces his wife must give her a certificate of divorce.
f 32But I tell you that anyone who divorces his wife, except for sexual immorality, makes her the victim of adultery, and anyone who marries a divorced woman commits adultery.
Oaths
33Again, you have heard that it was said to the people long ago, Do not break your oath, but fulfill to the Lord the vows you have made.
34But I tell you, do not swear an oath at all: either by heaven, for it is Gods throne;
35or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King.
36And do not swear by your head, for you cannot make even one hair white or black.
37All you need to say is simply Yes or No; anything beyond this comes from the evil one.
g
Eye for Eye
38You have heard that it was said, Eye for eye, and tooth for tooth.
h 39But I tell you, do not resist an evil person. If anyone slaps you on the right cheek, turn to them the other cheek also.
40And if anyone wants to sue you and take your shirt, hand over your coat as well.
41If anyone forces you to go one mile, go with them two miles.
42Give to the one who asks you, and do not turn away from the one who wants to borrow from you.
Love for Enemies
43You have heard that it was said, Love your neighbor
i and hate your enemy.
44But I tell you, love your enemies and pray for those who persecute you,
45that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous.
46If you love those who love you, what reward will you get? Are not even the tax collectors doing that?
47And if you greet only your own people, what are you doing more than others? Do not even pagans do that?
48Be perfect, therefore, as your heavenly Father is perfect.
1Then Jesus spoke to the crowds and to His disciples,
2saying: The scribes and the Pharisees have seated themselves in the chair of Moses;
3therefore all that they tell you, do and observe, but do not do according to their deeds; for they say
things and do not do
them. 4They tie up heavy burdens and lay them on mens shoulders, but they themselves are unwilling to move them with
so much as a finger.
5But they do all their deeds to be noticed by men; for they broaden their phylacteries and lengthen the tassels
of their garments. 6They love the place of honor at banquets and the chief seats in the synagogues,
7and respectful greetings in the market places, and being called Rabbi by men.
8But do not be called Rabbi; for One is your Teacher, and you are all brothers.
9Do not call
anyone on earth your father; for One is your Father, He who is in heaven.
10Do not be called leaders; for One is your Leader,
that is, Christ.
11But the greatest among you shall be your servant.
12Whoever exalts himself shall be humbled; and whoever humbles himself shall be exalted.