Jesus answered them, "Is it not written in your law, 'I said, you are gods'?" (John 10:34)
It is to fulfil the word that is written in their law, 'They hated me without a cause.' (John 15:25 RSV)
The Law of the Jews is not the Law of Christ!
This objection flies in the face of numerous other passages throughout the Bible in which God declares that the commandments are His (Exodus 20:6, Lev 22:31, Numbers 15:40, Deuteronomy 30:8, 10, etc) as well as the testimony that all of the Word of God is from God (John 1:1-2)! What is actually meant in these passages? Let's examine the context...
In John chapter 10, Jesus is responding to an accusation of blasphemy when He states that He and the Father are one (John 10:30). He reminds His Jewish accusers that they are called "gods" [Hebrew: elohim (which means rulers or judges)] in Psalm 82:6. If their poor behavior and judgment qualifies them to be called "gods" then how much more so is He, the perfectly obedient Son, qualified to be called elohim!
Christ's goal is not to declare "in your law 'X' is written but in my law 'Y' is written". He is pointing out to them that they, who claim to know and obey the Law fully, should already know that they are called elohim so it is not blasphemy for one who actually obeys God to be called His son. Indeed, the gospel of John declares those who believe are given the power to become children of God (John 1:12).
In John chapter 15, Messiah teaches His disciples "they hated me without a cause" and refers to "their law". This passage is a quote from either Psalm 35:19 or Psalm 69:4 (or possibly both) which prophetically speaks of Messiah's rejection by the leaders of His people. In essence, Messiah is telling them, "Don't worry about them or their rejection of Me. Their own Law says they would reject Me! This is supposed to happen."
Please note that the Lords's quotes do not come from the traditional "Law" of the Pentateuch (the so-called "Books of Moses") but from the Psalms! And yet He calls it "Law". Clearly all of Scripture is God's Law and teaching as Paul so eloquently put it in his second letter to Timothy:
All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work. (2 Timothy 3:16-17 emphasis added)
There is nothing in these passages that suggests Messiah is rejecting the Law of Moses. On the contrary, Messiah declares that He came not to abolish the Law but to give His followers the fullness of it (Matthew 5:17). May we rejoice in the gifts He has given to us!