Romans 10:1-13
Brethren, my heart's desire and prayer to God for Israel is, that they might be saved.
2For I bear them record that
they have a zeal of God, but not according to knowledge. 3For they being ignorant of God's righteousness, and going about to establish their own righteousness, have not submitted themselves unto the righteousness of God. 4For
Christ is the end of the law for righteousness to every one that believeth.
5For
Moses describeth the righteousness which is of the law, That the man which doeth those things shall live by them.
6But the righteousness which is of faith speaketh on this wise, Say not in thine heart, Who shall ascend into heaven? (that is, to bring Christ down
from above 7Or, Who shall descend into the deep? (that is, to bring up Christ again from the dead.)
8But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach; 9That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. 10For with the heart man believeth unto righteousness; and
with the mouth confession is made unto salvation. 11For the scripture saith,
Whosoever believeth on him shall not be ashamed. 12For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him.
13For whosoever shall call upon the name of the Lord shall be saved.
Jesus Christ is the only man who was able to fulfill the requirements of the law of Moses....... every iota.
Righteousness is imputed to man from God solely based on faith and not on works of the law of Moses. The law was a curse to make all men guilty before God, to cause them to surrender to God through faith in Christ after acknowledging they are guilty of sin and need God to save them (like David did). The people that received the law of Moses in the desert all died and without mercy because they weren't willing to live by faith but instead wanted instructions and got what they deserved, laws they could not keep that brought death for unbelief. If you teach men to follow the same laws of Moses to be justified......Christ is of no effect to you, you have become alienated from Him and have fallen from grace. Do you practice what you preach you who boast in the law? No, only outwardly at best but inside you are liars,covetous,murderers,adulterers, thieves,dishonorable to parents,love yourself more than God,idolaters, and everything you claim that you are not outwardly (let all men be liars and let God be true). God looks at the inside and says to Pharisees like you to clean the inside of the cup.
In the op you quoted Matthew 5. Take a good look at what Jesus is saying there (read thoroughly through the Greek as well). He is making clear that He is changing the law of Moses that He gave Moses at Sinai/Horeb. After Matthew 5 it became illegal to even think sin in your heart. It tightens the law of Moses to make all men guilty before God forever with the exception of Christ.
Repent and believe don't lie to yourself and attempt to deceive. Embrace the simplicity of Christ through faith working in love.