The Jews insisted, “We have a law, and according to that law he must die, because he claimed to be the Son of God.”
The Jews finally come to the heart of the matter. They had not previously mentioned the real reason for their wanting the death of Jesus because it was not a violation of Roman law, but now that Pilate had thrown into their faces the innocence of Jesus, they had to justify themselves and their actions by speaking the truth.
They use an emphatic pronoun of their own when they say “we”. Jesus had violated their law (Lev 24:16) by claiming to be the Son of God (John 5:18, 8:53, 10:33). This was why the Sanhedrin had voted for His death (Mark 14:61-64), although they conveniently neglected to disclose that particular fact to Pilate since they didn’t have the legal right to do so. Even worse, they were claiming that the law Jesus broke was that He claimed to be the Son of God and the fact is that He was, but they never bothered to have an open mind or to check His credentials. They were claiming they must obey their law and yet they were breaking their own law in order to uphold it (Rom 2:23). Do we ever do this?
Leviticus 24:16 anyone who blasphemes the name of the LORD must be put to death. The entire assembly must stone him. Whether an alien or native-born, when he blasphemes the Name, he must be put to death.
John 5:18 For this reason the Jews tried all the harder to kill him; not only was he breaking the Sabbath, but he was even calling God his own Father, making himself equal with God.
John 8:53 Are you greater than our father Abraham? He died, and so did the prophets. Who do you think you are?”
John 10:33 “We are not stoning you for any of these,” replied the Jews, “but for blasphemy, because you, a mere man, claim to be God.”
Mark 14:61-64 But Jesus remained silent and gave no answer. Again the high priest asked him, “Are you the Christ, the Son of the Blessed One?” “I am,” said Jesus. “And you will see the Son of Man sitting at the right hand of the Mighty One and coming on the clouds of heaven.” The high priest tore his clothes. “Why do we need any more witnesses?” he asked. “You have heard the blasphemy. What do you think?” They all condemned him as worthy of death.
Romans 2:23 You who brag about the law, do you dishonour God by breaking the law?