Because of mankind’s propensity to try and save ourselves and to create our own standards of righteousness and holiness and to try and distinguish good and evil in ourselves, the law of Moses came into the earth. The purpose of the law of Moses is to bring mankind to the end of themselves and realize their complete and utter dependence on God. It’s purpose is to kill and totally and completely condemn the old man and separation from God. It prevents any person from elevating themselves above another person. It shuts the mouth of anyone who would declare themselves to be righteous or holy and try to exalt themselves above other people.
Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God. For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin. (Romans 3:19-20)
When Jesus came to the earth, the Pharisees and some of the religious leaders of the day had watered down the law of Moses into something that they boasted that they could keep. Jesus came and highlighted the impossible standards of the law. In Matthew 5, Jesus says to us that if anyone is angry at his brother, that person is just as guilty as the murderer and anyone who has lust in their heart has committed adultery and is just as guilty as the adulterer. Jesus warned against relaxing any commandment of the law or teaching others to do likewise because the law and the prophets bring us to the end of ourselves and show us our complete and total dependence on God. No man can be justified by the law or keep the law of Moses and those who try remain under the condemnation or curse of the domain of darkness.
But now the righteousness of God has been manifested apart from the law, although the Law and the Prophets bear witness to it— the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction: for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus, (Romans 3:21-25)
Man cannot save other men, nor can we save ourselves by following the law of Moses or by doing good deeds. We are saved from the wrath of the law and the wages of sin ONLY by faith in Jesus Christ.
For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, NOT a result of works so that no one can boast. (Ephesians 2:8-9)
And there is salvation in no one else besides Jesus, for there is no other name under heaven given among men by which we must be saved (Acts 4:12)
because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved. (Romans 10:9-10)