Assuming one is a devout Jew—like Jesus, and is faithful to all Mitzvot in the Torah—i.e. the Five Books of Moses, thus is without sin. Contained in the Christians’ “Greek Old Testament,”
Why is there a need for the New Testament—expounding belief in a Messiah, who has yet to appear to protect us? Per Numbers 24;17 & Deuteronomy 18;18.
Jesus is the only person without sin. This is because Jesus does not have a human father. Jesus is the only person in all of eternity who is fully God and fully man (John 1:1-2; 14; Philippians 2:5-11; Colossians 1:15-18). Our sin nature is passed down to us from Adam through our fathers. Thus, we are sinners by nature and we sin by choice. “All have sinned and fall short of the glory of God” (Romans 3:23).
In John 8:46 Jesus asked His opponents, “Can any of you prove me guilty of sin?” Those who were against Him would certainly have pointed out sin in Jesus’ life if they could. They watched Jesus closely, looking for ways to discredit Him. They could not do it.
Being faithful to the Torah does not mean a person can say that they are sin free. A person who is faithful to the Torah must offer sacrifices for sin. The problem is that the sacrifices required in the Torah cannot take away sin. Hebrews 10:11 says, “Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices, which can never take away sins.”
The sacrifices required in the Torah prepared the way for the ultimate sacrifice that God’s Son would make when He died on the cross. Think of the Old Testament sacrificial system as a preview of what was to come.
When Jesus hung on the cross, God the Father accepted His sacrifice on our behalf as full payment for our sin. Jesus cried out from the cross, “It is finished!” (John 19:30); which means “it is paid in full.” Therefore, when we repent of our sins and place our trust in Jesus as our Redeemer we are forgiven and we gain eternal life (John 3:16-17; 5:24).
It has been said that the New Testament is the Old Testament revealed. In other words, the New Testament explains the Old Testament by telling us about Jesus the Messiah who fulfilled everything the Old Testament was pointing toward. Jesus said it this way, “Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them” (Matthew 5:17).