I contended that that's why the Pharisees and Sadducees hated him so much. His teachings undermined the religious system that had developed over hundreds of years. Not only did his teachings undermine the religious system, but the authority with which Jesus taught sent a clear message as to how Jesus viewed his legitimacy and his ability to refine the sacred texts of Israel.
Jesus spoke with certainty and confidence. He taught the people truths about God without the approval of the religious leaders. Even the common people noticed this.
Matthew 7:28-298When Jesus had finished saying these things, the crowds were amazed at his teaching, 29because he taught as one who had authority, and not as their teachers of the law.
"By whose authority do you do these things?" the Pharisees often asked.
Matthew 21:23-2723Jesus entered the temple courts, and, while he was teaching, the chief priests and the elders of the people came to him. "By what authority are you doing these things?" they asked. "And who gave you this authority?"
24Jesus replied, "I will also ask you one question. If you answer me, I will tell you by what authority I am doing these things. 25John's baptism—where did it come from? Was it from heaven, or from men?"
They discussed it among themselves and said, "If we say, 'From heaven,' he will ask, 'Then why didn't you believe him?' 26But if we say, 'From men'—we are afraid of the people, for they all hold that John was a prophet."
27So they answered Jesus, "We don't know."
Then he said, "Neither will I tell you by what authority I am doing these things.
The religious leaders, who described themselves as disciples of Moses, could never authoritatively alter the Law. They could only parse and debate its meaning, attempting to fit it into their current circumstances. They couldn't relate a higher standard than what they already had in the Law, because to do so would imply that the Law was insufficient....which is exactly what the New Testament teaches.
Galatians 3:19-2519What, then, was the purpose of the law? It was added because of transgressions until the Seed to whom the promise referred had come. The law was put into effect through angels by a mediator. 20A mediator, however, does not represent just one party; but God is one.
21Is the law, therefore, opposed to the promises of God? Absolutely not! For if a law had been given that could impart life, then righteousness would certainly have come by the law. 22But the Scripture declares that the whole world is a prisoner of sin, so that what was promised, being given through faith in Jesus Christ, might be given to those who believe.
23Before this faith came, we were held prisoners by the law, locked up until faith should be revealed. 24So the law was put in charge to lead us to Christ that we might be justified by faith. 25Now that faith has come, we are no longer under the supervision of the law.
Ephesians 2:14-15a14For he himself is our peace, who has made the two one and has destroyed the barrier, the dividing wall of hostility, 15by abolishing in his flesh the law with its commandments and regulations.
Hebrews 10:1The law is only a shadow of the good things that are coming—not the realities themselves. For this reason it can never, by the same sacrifices repeated endlessly year after year, make perfect those who draw near to worship.
To put all of this together we need to understand that the story of Scripture is an evolving revelation of humans interacting with the Divine. The Israelites under Moses had more experience with the Divine than they did before Moses. The Israelites hundreds of years after Moses had further experiences which informed their views about God. It is a progressive accumulation and refinement of how a particular people understood God and his relationship with people.
To say that maybe not everything in the Mosaic code was straight from God is not to denigrate it. Instead, by understanding it in terms of a path eventually leading to Jesus, we affirm Jesus' message. We affirm that God works on purifying His people from the inside out, through his indwelling Spirit, rather than through external actions.
This is what is meant by John 4:23:
23Yet a time is coming and has now come when the true worshipers will worship the Father in spirit and truth, for they are the kind of worshipers the Father seeks.
Admitting the human dynamic in the formation of Scripture does not subtract from God, but instead affirms that He is higher than we limited beings are capable of expressing adequately.